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Condensed Matter

New submissions

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New submissions for Tue, 20 Mar 18

[1]  arXiv:1803.06342 [pdf, ps, other]
Title: 3D modelling of macroscopic force-free effects in superconducting thin films and rectangular prisms
Comments: 31 pages, 20 figures
Subjects: Superconductivity (cond-mat.supr-con)

When the magnetic field has a parallel component to the current density ${\bf J}$ there appear force-free effects due to flux cutting and crossing. This results in an anisotropic ${\bf E}({\bf J})$ relation, being ${\bf E}$ the electric field. Understanding force-free effects is interesting not only for the design of superconducting power and magnet applications but also for material characterization.
This work develops and applies a fast and accurate computer modeling method based on a variational approach that can handle force-free anisotropic ${\bf E}({\bf J})$ relations and perform fully three dimensional (3D) calculations. We present a systematic study of force-free effects in rectangular thin films and prisms with several finite thicknesses under applied magnetic fields with arbitrary angle $\theta$ with the surface. The results are compared with the same situation with isotropic ${\bf E}({\bf J})$ relation.
The thin film situation shows gradual critical current density penetration and a general increase of the magnitude of the magnetization with the angle $\theta$ but a minimum at the remnant state of the magnetization loop. The prism model presents current paths with 3D bending for all angles $\theta$. The average current density over the thickness agrees very well with the thin film model except for the highest angles. The prism hysteresis loops reveal a peak after the remnant state, which is due to the parallel component of the self-magnetic-field and is implicitly neglected for thin films.
The presented numerical method shows the capability to take force-free situations into account for general 3D situations with a high number of degrees of freedom. The results reveal new features of force-free effects in thin films and prisms.

[2]  arXiv:1803.06349 [pdf, other]
Title: Two-Dimensional Dirac Nodal-Loop Magnons in Collinear Antiferromagnets
Authors: S. A. Owerre
Comments: 4 pages, 3 figures
Subjects: Strongly Correlated Electrons (cond-mat.str-el)

We study the nontrivial magnon band crossings in the collinear antiferromagnets on the two-dimensional (2D) CaVO lattice. It is shown that the combination of space-inversion and time-reversal symmetry ($\mathcal{PT}$-symmetry) leads to doubly-degenerate eight magnon branches, which cross each other along a one-dimensional loop in the 2D Brillouin zone. We show that the Dirac nodal-loops (DNLs) are not present in the collinear ferromagnet on this lattice. Thus, the current 2D antiferromagnetic DNLs are symmetry-protected and they provide a novel platform to search for their analogs in 2D electronic antiferromagnetic systems.

[3]  arXiv:1803.06364 [pdf, other]
Title: Conversion rules for Weyl points and nodal lines in topological media
Comments: Main text (4 pages, 4 figures) + Supplement (17 pages, 7 figures)
Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)

According to a widely-held paradigm, a pair of Weyl points with opposite chirality mutually annihilate when brought together. In contrast, we show that such a process is strictly forbidden for Weyl points related by a mirror symmetry, provided that an effective two-band description exists in terms of orbitals with opposite mirror eigenvalue. Instead, such a pair of Weyl points converts into a nodal loop inside a symmetric plane upon the collision. Similar constraints are identified for systems with multiple mirrors, facilitating previously unreported nodal-line and nodal-chain semimetals that exhibit both Fermi-arc and drumhead surface states. We further find that Weyl points in systems symmetric under a $\pi$-rotation composed with time-reversal are characterized by an additional integer charge that we term vorticity. A pair of Weyl points with opposite chirality can annihilate only if their vorticities also cancel out. We base our predictions on topological crystalline invariants derived from relative homotopy theory, and we test our predictions on simple tight-binding models. The outlined homotopy description can be directly generalized to systems with multiple bands and other choices of symmetry.

[4]  arXiv:1803.06374 [pdf, other]
Title: Ab Initio Electron-Phonon Interactions Using Atomic Orbital Wavefunctions
Subjects: Materials Science (cond-mat.mtrl-sci)

The interaction between electrons and lattice vibrations determines key physical properties of materials, including their electrical and heat transport, excited electron dynamics, phase transitions, and superconductivity. We present a new ab initio method that employs atomic orbital (AO) wavefunctions to compute the electron-phonon (e-ph) interactions in materials and interpolate the e-ph coupling matrix elements to fine Brillouin zone grids. We detail the numerical implementation of such AO-based e-ph calculations, and benchmark them against direct density functional theory calculations and Wannier function (WF) interpolation. The key advantages of AOs over WFs for e-ph calculations are outlined. Since AOs are fixed basis functions associated with the atoms, they circumvent the need to generate a material-specific localized basis set with a trial-and-error approach, as is needed in WFs. Therefore, AOs are ideal to compute e-ph interactions in chemically and structurally complex materials for which WFs are challenging to generate, and are also promising for high-throughput materials discovery. While our results focus on AOs, the formalism we present generalizes e-ph calculations to arbitrary localized basis sets, with WFs recovered as a special case.

[5]  arXiv:1803.06388 [pdf, other]
Title: Pressure-Tunable Photonic Band Gaps in an Entropic Colloidal Crystal
Comments: 6 REVTeX pages, 4 figures
Subjects: Materials Science (cond-mat.mtrl-sci); Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Soft Condensed Matter (cond-mat.soft)

Materials adopting the diamond structure possess useful properties in atomic and colloidal systems, and are a popular target for synthesis in colloids where a photonic band gap is possible. The desirable photonic properties of the diamond structure pose an interesting opportunity for reconfigurable matter: can we create a colloidal crystal able to switch reversibly to and from the diamond structure? Drawing inspiration from high-pressure transitions of diamond-forming atomic systems, we design a system of polyhedrally-shaped particles that transitions from diamond to a tetragonal diamond derivative upon a small pressure change. The transition can alternatively be triggered by changing the shape of the particle in-situ. We propose that the transition provides a reversible reconfiguration process for a potential new colloidal material, and draw parallels between this transition and phase behavior of the atomic transitions from which we take inspiration.

[6]  arXiv:1803.06404 [pdf, other]
Title: Helical Network Model for Twisted Bilayer Graphene
Comments: 6 pages and 4 figures
Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)

In the presence of a finite interlayer displacement field bilayer graphene has an energy gap that is dependent on stacking and largest for the stable AB and BA stacking arrangements. When the relative orientations between layers are twisted through a small angle to form a moir$\mathrm{\acute{e}}$ pattern, the local stacking arrangement changes slowly. We show that for non-zero displacement fields the low-energy physics of twisted bilayers is captured by a phenomenological helical network model that describes electrons localized on domain walls separating regions with approximate AB and BA stacking. The network band structure is gapless and has of a series of two-dimensional bands with Dirac band-touching points and a density-of-states that is periodic in energy with one zero and one divergence per period.

[7]  arXiv:1803.06405 [pdf]
Title: Control of interlayer excitons in two-dimensional van der Waals heterostructures
Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)

Long-lived interlayer excitons with distinct spin-valley physics in van der Waals heterostructures based on transition metal dichalcogenides make them promising for information processing in next-generation devices. While the emission characteristics of interlayer excitons in different types of hetero stacks have been extensively studied, the manipulation of these excitons required to alter the valley-state or tune the emission energy and intensity is still lacking. Here, we demonstrate such control over interlayer excitons in MoSe2/WSe2 heterostructures. The encapsulation of our stack with h-BN ensures ultraclean interfaces, allowing us to resolve four separate narrow interlayer emission peaks. We observe two main interlayer transitions with opposite helicities under circularly polarized excitation, either conserving or inverting the polarization of incoming light. We further demonstrate control over the wavelength, intensity, and polarization of exciton emission by electrical and magnetic fields. Such ability to manipulate the interlayer excitons and their polarization could pave the way for novel excitonic and valleytronic device applications.

[8]  arXiv:1803.06424 [pdf, other]
Title: Thermal entanglement in the mixed-spin Ising-Heisenberg double sawtooth frustrated ladder
Comments: Submitted to Solid State communications, 13 pages, 6 figures
Subjects: Statistical Mechanics (cond-mat.stat-mech)

The entanglement between spin-1/2 interstitial Heisenberg dimers in the mixed spin-(1,1/2) Ising-XXZ double sawtooth ladder is investigated at low temperature. Here, we consider a cyclic four-spin exchange interaction in square plaquette of each block, and investigate the effects of this amazing interaction on the bipartite entanglement between spin-1/2 interstitial dimers. Interestingly, we observe a remarkable difference in concurrence behavior with respect to the cyclic four-spin exchange interaction and magnetic field. Also, the critical points at which the concurrence vanishes are changed versus alteration of the anisotropic parameter of the interstitial Heisenberg dimers.

[9]  arXiv:1803.06425 [pdf, other]
Title: Reinforcement Learning of Artificial Microswimmers
Subjects: Soft Condensed Matter (cond-mat.soft); Biological Physics (physics.bio-ph)

The behavior of living systems is based on the experience they gained through their interactions with the environment [1]. This experience is stored in the complex biochemical networks of cells and organisms to provide a relationship between a sensed situation and what to do in this situation [2-4]. An implementation of such processes in artificial systems has been achieved through different machine learning algorithms [5, 6]. However, for microscopic systems such as artificial microswimmers which mimic propulsion as one of the basic functionalities of living systems [7, 8] such adaptive behavior and learning processes have not been implemented so far. Here we introduce machine learning algorithms to the motion of artificial microswimmers with a hybrid approach. We employ self-thermophoretic artificial microswimmers in a real world environment [9, 10] which are controlled by a real-time microscopy system to introduce reinforcement learning [11-13]. We demonstrate the solution of a standard problem of reinforcement learning - the navigation in a grid world. Due to the size of the microswimmer, noise introduced by Brownian motion if found to contribute considerably to both the learning process and the actions within a learned behavior. We extend the learning process to multiple swimmers and sharing of information. Our work represents a first step towards the integration of learning strategies into microsystems and provides a platform for the study of the emergence of adaptive and collective behavior.

[10]  arXiv:1803.06426 [pdf, ps, other]
Title: Entanglement in a fermionic spin chain containing a single boson under decoherence
Comments: 17 pages, 8 figures
Subjects: Statistical Mechanics (cond-mat.stat-mech); Quantum Physics (quant-ph)

The concurrence between the first and the last parts of a fermionic spin chain containing a single boson is investigated at finite low temperature in the vicinity of a weak homogeneous magnetic field. We consider different positions for the boson in the chain and study concurrence without/under decoherence and express some interesting phase flip and bit flip reactions of the pairwise entanglement between first and the last half-spins of the chain. Our investigations show that the concurrence between two half-spins has different behavior for various positions of the single boson along the chain. Indeed, we realize that the position of the single boson has an essential role to probe the pairwise entanglement between two spins located at the ends of a fermionic chain. Interestingly, the entanglement remains alive for higher temperatures when the boson is adjacent to the first site of the chain.

[11]  arXiv:1803.06428 [pdf, ps, other]
Title: Intrinsic spin-orbit torque in an antiferromagnet with weakly noncollinear spin configuration
Comments: 8 pages, 6 figures
Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)

An antiferromagnet is a promising material for spin-orbit torque generation. Earlier studies of the spin-orbit torque in an antiferromagnet are limited to collinear spin configurations. We calculate the spin-orbit torque in an antiferromagnet whose spin ordering is weakly noncollinear. Such noncollinearity may be induced spontaneously during the magnetization dynamics even when the equilibrium spin configuration is perfectly collinear. It is shown that deviation from perfect collinearity can modify properties of the spin-orbit torque since noncollinearity generates extra Berry phase contributions to the spin-orbit torque, which are forbidden for collinear spin configurations. In sufficiently clean antiferromagnets, this modification can be significant. We estimate this effect to be of relevance for fast antiferromagnetic domain wall motion.

[12]  arXiv:1803.06433 [pdf]
Title: Thermal conduction of one-dimensional carbon nanomaterials and nanoarchitectures
Comments: 10 pages, 10 figures
Journal-ref: Chin. Phys. B, 2018, 27 (3): 038103
Subjects: Materials Science (cond-mat.mtrl-sci); Applied Physics (physics.app-ph)

This review summarizes the current studies of the thermal transport properties of one-dimensional (1D) carbon nanomaterials and nanoarchitectures. Considering different hybridization states of carbon, emphases are laid on a variety of 1D carbon nanomaterials, such as diamond nanothreads, penta-graphene nanotubes, supernanotubes, and carbyne. Based on experimental measurements and simulation/calculation results, we discuss the dependence of the thermal conductivity of these 1D carbon nanomaterials on a wide range of factors, including the size effect, temperature influence, strain effect, and others. This review provides an overall understanding of the thermal transport properties of 1D carbon nanomaterials and nanoarchitectures, which paves the way for effective thermal management at nanoscale.

[13]  arXiv:1803.06435 [pdf]
Title: Chapter 7 - Thermal Conductivity of Diamond Nanothread
Comments: 19 pages, 13 figures
Journal-ref: A volume in Micro and Nano Technologies, 2017, Pages 185-204
Subjects: Materials Science (cond-mat.mtrl-sci); Applied Physics (physics.app-ph)

This chapter introduces the thermal conductivity of a novel one-dimensional carbon nanostructure - diamond nanothread. It starts by introducing the family of the diamond nanothread as acquired from density functional theory calculations and also its successful experimental synthesisation. It then briefs the mechanical properties of the diamond nanothreads as a fundamental for their engineering applications. After that, it focuses on the thermal transport properties of the diamond nanothreads by examining the influences from various parameters such as size, geometry, and temperature. Then, the application of diamond nanothread as reinforcements for nanocomposites is discussed. By the end of the chapter, future directions and their potential applications are discussed.

[14]  arXiv:1803.06437 [pdf]
Title: Graphene and Carbon Nanotube Hybrid Structure: A Review
Comments: 8 pages, 7 figures
Journal-ref: Procedia IUTAM,Volume 21, 2017, Pages 94-101
Subjects: Materials Science (cond-mat.mtrl-sci); Applied Physics (physics.app-ph)

Graphene has been reported with record-breaking properties which have opened up huge potential applications. Considerable amount of researches have been devoted to manipulating or modify the properties of graphene to target a more smart nanoscale device. Graphene and carbon nanotube hybrid structure (GNHS) is one of the promising graphene derivate. The synthesis process and the mechanical properties are essential for the GNHS based devices. Therefore, this review will summarise the recent progress of the highly ordered GNHS synthesis/assembly, and discuss the mechanical properties of GNHS under various conditions as obtained from molecular dynamics simulations.

[15]  arXiv:1803.06438 [pdf]
Title: The morphology and temperature dependent tensile properties of diamond nanothreads
Comments: 6 pages, 6 figures
Journal-ref: Carbon,Volume 107, October 2016, Pages 304-309
Subjects: Materials Science (cond-mat.mtrl-sci)

The ultrathin one-dimensional sp3 diamond nanothreads (NTHs), as successfully synthesised recently, have greatly augmented the interests from the carbon community. In principle, there can exist different stable NTH structures. In this work, we studied the mechanical behaviours of three representative NTHs using molecular dynamics simulations. It is found that the mechanical properties of NTH can vary significantly due to morphology differences, which are believed to originate from the different stress distributions determined by its structure. Further studies have shown that the temperature has a significant impact on the mechanical properties of the NTH. Specifically, the failure strength/strain decreases with increasing temperature, and the effective Young's modulus appears independent of temperature. The remarkable reduction of the failure strength/strain is believed to be resulted from the increased bond re-arrangement process and free lateral vibration at high temperatures. In addition, the NTH is found to have a relatively high bending rigidity, and behaves more like flexible elastic rod. This study highlights the importance of structure-property relation and provides a fundamental understanding of the tensile behaviours of different NTHs, which should shed light on the design and also application of the NTH-based nanostructures as strain sensors and mechanical connectors.

[16]  arXiv:1803.06440 [pdf]
Title: Failure mechanism of monolayer graphene under hypervelocity impact of spherical projectile
Comments: 10 pages, 9 figures
Journal-ref: Scientific Reports volume 6, Article number: 33139 (2016)
Subjects: Materials Science (cond-mat.mtrl-sci); Applied Physics (physics.app-ph)

The excellent mechanical properties of graphene have enabled it as appealing candidate in the field of impact protection or protective shield. By considering a monolayer graphene membrane, in this work, we assessed its deformation mechanisms under hypervelocity impact (from 2 to 6 km/s), based on a serial of in silico studies. It is found that the cracks are formed preferentially in the zigzag directions which are consistent with that observed from tensile deformation. Specifically, the boundary condition is found to exert an obvious influence on the stress distribution and transmission during the impact process, which eventually influences the penetration energy and crack growth. For similar sample size, the circular shape graphene possesses the best impact resistance, followed by hexagonal graphene membrane. Moreover, it is found the failure shape of graphene membrane has a strong relationship with the initial kinetic energy of the projectile. The higher kinetic energy, the more number the cracks. This study provides a fundamental understanding of the deformation mechanisms of monolayer graphene under impact, which is crucial in order to facilitate their emerging future applications for impact protection, such as protective shield from orbital debris for spacecraft.

[17]  arXiv:1803.06442 [pdf, other]
Title: Replica Symmetry Breaking in Bipartite Spin Glasses and Neural Networks
Comments: 32 pages, 14 figures
Subjects: Disordered Systems and Neural Networks (cond-mat.dis-nn); Learning (cs.LG)

Some interesting recent advances in the theoretical understanding of neural networks have been informed by results from the physics of disordered many-body systems. Motivated by these findings, this work uses the replica technique to study the mathematically tractable bipartite Sherrington-Kirkpatrick (SK) spin glass model, which is formally similar to a Restricted Boltzmann Machine (RBM) neural network. The bipartite SK model has been previously studied assuming replica symmetry; here this assumption is relaxed and a replica symmetry breaking analysis is performed. The bipartite SK model is found to have many features in common with Parisi's solution of the original, unipartite SK model, including the existence of a multitude of pure states which are related in a hierarchical, ultrametric fashion. As an application of this analysis, the optimal cost for a graph partitioning problem is shown to be simply related to the ground state energy of the bipartite SK model. As a second application, empirical investigations reveal that the Gibbs sampled outputs of an RBM trained on the MNIST data set are more ultrametrically distributed than the input data itself.

[18]  arXiv:1803.06447 [pdf, ps, other]
Title: Emergence of spin-orbit order in the spinel CuCr$_2$O$_4$
Subjects: Strongly Correlated Electrons (cond-mat.str-el)

We determined the magnetic structure of CuCr$_2$O$_4$ using neutron diffraction and irreducible representation analysis. The measurements identified a new phase between 155 K and 125 K as nearly collinear magnetic ordering in the Cr pyrochlore lattice. Below 125 K, a Cu-Cr ferrimagnetic component develops the noncollinear order. Along with the simultaneously obtained O positions and the quantum effect of spin-orbit coupling, the magnetic structure is understood to involve spin-orbit ordering, accompanied by an appreciably deformed orbital of presumably spin-only Cu and Cr.

[19]  arXiv:1803.06474 [pdf, ps, other]
Title: Finite-Size Scaling Regarding Interaction in the Many-Body Localization Transition
Comments: 4 pages, 3 figures
Subjects: Disordered Systems and Neural Networks (cond-mat.dis-nn); Statistical Mechanics (cond-mat.stat-mech); Quantum Physics (quant-ph)

We present a novel finite-size scaling for both interaction and disorder strengths in the critical regime of the many-body localization (MBL) transition for a spin-1/2 XXZ spin chain with random field by studying the level statistics. We show how the dynamical transition from the thermal to MBL phase depends on interaction together with disorder by evaluating the adjacent gap ratio, and thus, extend previous studies in which the interaction coupling is fixed. We introduce an extra critical exponent in order to describe the nontrivial interaction dependence of the MBL transition. It is characterized by the ratio of the disorder strength to the power of the interaction coupling with respect to the extra critical exponent and not by the simple ratio between them.

[20]  arXiv:1803.06475 [pdf, other]
Title: Magneto-optical trapping of optically pumped metastable europium
Comments: 5 pages, 5 figures
Subjects: Quantum Gases (cond-mat.quant-gas); Atomic Physics (physics.atom-ph)

The laser cooling and trapping of europium is demonstrated herein. The atoms are optically pumped to a metastable state and then loaded from an atomic-beam source via conventional Zeeman slowing and magneto-optical trapping techniques using a J=13/2 <--> J=15/2 quasi-cyclic transition. The trapped populations contained up to 1x10^7 atoms, and the density-dependent loss rate is estimated as 1x10^-10 cm^3/s from the non-exponential loss of atoms at high densities. We also observed leakage out of the quasi-cyclic transition to the J=9/2 and 11/2 metastable states, which is adequate to pump the laser-cooled atoms back to the ground state.

[21]  arXiv:1803.06485 [pdf, ps, other]
Title: Impact of Dzyaloshinsky-Moriya Interactions and Tilts of the g Tensors on the Magnetization Process of a Spherical Kagome Cluster in {W72V30}
Comments: 6 pages, 7 figures
Subjects: Strongly Correlated Electrons (cond-mat.str-el)

In order to clarify why the experimental magnetization curve of the spherical kagome cluster in {W72V30} at 0.5 K shows no sign of staircase behavior up to 50 T, we study the effects of Dzyaloshinsky-Moriya (DM) interactions and tilts of the g tensors, both of which lead to the breaking of the total-S z conservation, by using the exact diagonalization method. It is found that the D vector component parallel to the radiation direction of the polyhedron cancels out the staircase in a low magnetic field region efficiently. The tilts of the g tensors are inherent to systems defined on the poly- hedrons and lead to induced magnetic fields varying site by site. This induced magnetic field affects the magnetization only at high magnetic fields. We also discuss two existing experimental results on the basis of our calculated results.

[22]  arXiv:1803.06489 [pdf]
Title: Experimental evidences of trions and Fermi edge singularity in single barrier GaAs/AlAs/GaAs heterostructure using photocapacitance spectroscopy
Comments: 28 pages including 5 figures
Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Quantum Gases (cond-mat.quant-gas)

In this paper, we show how photocapacitance spectra can probe two dimensional excitonic complexes and Fermi edge singularity as a function of applied bias around 100 K. In lower density regimes (<1x1011cm^-2), the appearance of two distinct peaks in the spectra are identified as a signature of coexistence of both excitons and positively charged trions. We estimate the binding energy of these trions as ~2.0 meV. In the higher density regimes (>1x10^11 cm^-2), we observe a sharp spectral transition from trions to asymmetric shaped Fermi edge singularity in the photocapacitance spectra around a particular reverse bias. However, these signatures are absent from the photoluminescence spectra measured under identical circumstances. Such dissimilarities clearly point out that different many body physics govern these two spectral measurements. We also argue why such quantum confined dipoles of spatially indirect trions can have thermodynamically finite probability to survive even around 100 K. Finally, our observations demonstrate that photocapacitance technique, which was seldom used to detect trions in the past, can also be useful to detect the traces of these spatially indirect excitonic complexes as well as Fermi edge singularity even at 100 K. This is mainly due to enhanced sensitivity of such dielectric measurements to dipolar changes within such heterojunction.

[23]  arXiv:1803.06495 [pdf, other]
Title: Superior mechanical flexibility and strained-engineered direct-indirect band gap transition of green phosphorene
Comments: 5 pages, 5 figures
Subjects: Materials Science (cond-mat.mtrl-sci)

Most recently, a brand new phosphorus allotrope called green phosphorus has been predicted, which has a direct band gap up to 2.4 eV, and its single-layer form termed green phosphorene shows high stability. Here the mechanical properties and the uniaxial strain effect on the electronic band structure of green phosphorene along two perpendicular in-plane directions are investigated. Remarkably, we find that this material can sustain a tensile strain in the armchair direction up to a threshold of 35\% which is larger than that of black phosphorene, suggesting that green phosphorene is more puckered. Our calculations also show the Young's modulus and Poisson's ratio in the zigzag direction are four times larger than those in the armchair direction, which confirm the anisotropy of the material. Furthermore, the uniaxial strain can trigger the direct-indirect band gap transition for green phosphorene and the critical strains for the band gap transition are revealed.

[24]  arXiv:1803.06504 [pdf, other]
Title: Superconductivity without inversion and time-reversal symmetries
Subjects: Superconductivity (cond-mat.supr-con)

The traditional symmetries that protect superconductivity are time-reversal and inversion. Here, we examine the minimal symmetries protecting superconductivity in two dimensions and find that time-reversal symmetry and inversion symmetry are not required, and having a combination of either symmetry with a mirror operation on the basal plane is sufficient. We classify superconducting states stabilized by these two symmetries, when time-reversal and inversion symmetries are not present, and provide realistic minimal models as examples. Interestingly, several experimentally realized systems, such as transition metal dichalcogenides and the two-dimensional Rashba system belong to this category, when subject to an applied magnetic field.

[25]  arXiv:1803.06512 [pdf]
Title: Quantum engineering of transistors based on 2D materials heterostructures
Comments: 15 pages, 4 figures
Journal-ref: Nature Nanotechnology Vol. 13, pp. 183-191, 2018
Subjects: Materials Science (cond-mat.mtrl-sci); Mesoscale and Nanoscale Physics (cond-mat.mes-hall)

Quantum engineering entails atom by atom design and fabrication of electronic devices. This innovative technology that unifies materials science and device engineering has been fostered by the recent progress in the fabrication of vertical and lateral heterostructures of two-dimensional materials and by the assessment of the technology potential via computational nanotechnology. But how close are we to the possibility of practical realisation of the next generation atomically thin transistors? In this perspective we analyse the outlook and the challenges of quantum- engineered transistors using heterostructures of two-dimensional materials against the benchmark of silicon technology and its foreseeable evolution in terms of potential performance and manufacturability. Transistors based on lateral heterostructures emerge as the most promising option from a performance point of view, even if heterostructure formation and control are in the initial technology development stage.

[26]  arXiv:1803.06528 [pdf]
Title: Optical properties of dense zirconium and tantalum diborides for solar thermal absorbers
Journal-ref: Renewable Energy, volume 91 (2016) pages 340-346
Subjects: Materials Science (cond-mat.mtrl-sci)

Ultra-high temperature ceramics (UHTCs) are interesting materials for a large variety of applications under extreme conditions. This paper reports on the production and extensive characterization of highly dense, pure zirconium and tantalum diborides, with particular interest to their potential utilization in the thermal solar energy field. Monolithic bulk samples are produced by Spark Plasma Sintering starting from elemental reactants or using metal diboride powders previously synthesized by Self-propagating High-temperature Synthesis (SHS). Microstructural and optical properties of products obtained by the two processing methods have been comparatively evaluated. We found that pure diborides show a good spectral selectivity, which is an appealing characteristic for solar absorber applications. No, or very small, differences in the optical properties have been evidenced when the two investigated processes adopted for the fabrication of dense TaB2 and ZrB2, respectively, are compared.

[27]  arXiv:1803.06538 [pdf]
Title: Interaction between stimulated current injection and polariton condensate
Comments: proceedings version of arXiv:1710.10920
Journal-ref: Proc. SPIE 10526, Physics and Simulation of Optoelectronic Devices XXVI, 105260H (2018)
Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)

In this paper, we see a strong effect of the injected current on the light emission from the polariton condensate in an n-i-n structure, when we monitor the luminescence intensity under applied bias at various pump powers. We present here three thresholds for nonlinear increase of the intensity. We show that small changes of the incoherent injected current lead to stimulated enhancement of the coherent light emission from free carriers. We conclude that the polariton condensate-current system is a highly nonlinear electro-optical system.

[28]  arXiv:1803.06544 [pdf, ps, other]
Title: Long ligands reinforce biological adhesion under shear flow
Subjects: Soft Condensed Matter (cond-mat.soft); Biological Physics (physics.bio-ph); Cell Behavior (q-bio.CB)

In the present work the computer modelling was used to show that longer ligands allow biological cells (e.g. blood platelets) to withstand stronger flows after their adhesion to solid walls. Mechanistic model of polymer-mediated ligand-receptor adhesion between a microparticle (cell) and a flat wall was developed. Theoretical threshold between adherent and non-adherent regimes was derived analytically and approved by the simulations. These results lead to deeper understanding of numerous biophysical processes, e.g. arterial thrombosis, and to the design of new biomimetic colloid-polymer systems.

[29]  arXiv:1803.06558 [pdf, other]
Title: Insensitivity of bulk properties to the twisted boundary condition
Authors: Haruki Watanabe
Comments: 5+7 pages, 1 figure
Subjects: Statistical Mechanics (cond-mat.stat-mech); Strongly Correlated Electrons (cond-mat.str-el)

The symmetry and the locality are the two major sources of various nontrivial statements in quantum many- body systems. We demonstrate that, in gapped phases of a U(1) symmetric Hamiltonian with finite-range interactions, the bulk properties such as the expectation value of local operators, the ground state energy and the excitation gap, and the static and low-frequency dynamical responses in general, do not depend on the U(1) phase of the twisted boundary condition in the limit of the large system size. Specifically, their dependence on the twisted angle is exponentially suppressed with the linear dimension of the system. The argument is based on the exponential decay of various types of equal-time correlation functions.

[30]  arXiv:1803.06564 [pdf, other]
Title: Nanoscale periodic domain patterns in tetragonal ferroelectrics: A phase-field study
Comments: 13 pages, 14 figures, 2 tables
Journal-ref: Physical Review B, 93(17), 174120 (2016)
Subjects: Materials Science (cond-mat.mtrl-sci)

Ferroelectrics form domain patterns that minimize their energy subject to imposed boundary conditions. In a linear, constrained theory, that neglects domain wall energy, periodic domain patterns in the form of multi-rank laminates can be identified as minimum-energy states. However, when these laminates (formed in a macroscopic crystal) comprise domains that are a few nanometers in size, the domain-wall energy becomes significant, and the behaviour of laminate patterns at this scale is not known. Here, a phase-field model, which accounts for gradient energy and strain energy contributions, is employed to explore the stability and evolution of the nanoscale multi-rank laminates. The stress, electric field, and domain wall energies in the laminates are computed. The effect of scaling is also discussed. In the absence of external loading, stripe domain patterns are found to be lower energy states than the more complex, multi-rank laminates, which mostly collapse into simpler patterns. However, complex laminates can be stabilized by imposing external loads such as electric field, average strain and polarization. The study provides insight into the domain patterns that may form on a macroscopic single crystal but comprising of nanoscale periodic patterns, and on the effect of external loads on these patterns.

[31]  arXiv:1803.06565 [pdf, other]
Title: Effect of Electron-RBM Phonon Interaction on Conductance of carbon nanotubes
Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Materials Science (cond-mat.mtrl-sci)

We use the energy analysis as a perturbative method to study the effect of electron-radial breathing mode (RBM) phonon interaction on the electrical conductivity of long metallic zigzag carbon nanotubes (CNTs). The band structure of zigzag CNTs is calculated by exerting zone-folding method on relations derived by using the nearest neighbor approximation of tight-binding expression for the $\pi$ valence and conduction bands of graphene. The small hollow cylinder model, with two different approximations, is used to obtain the RBM frequency in our calculation. As the result, we have calculated the effects of electron$ - $RBM phonon interaction on the conductance of zigzag CNTs. It has been observed that current is a step$ - $like function of bias voltage because of the absorption or emission by electron injection in the system. Moreover, the dependence of the conductance to the temperature in low bias and high bias voltages has been studied. In this paper, we propose a simple and useful method for phonon spectroscopy. Also, since RBM mode determines the geometry and structure of CNT, this approach can be used for characterization of CNTs.

[32]  arXiv:1803.06569 [pdf]
Title: On-Demand Generation of Neutral and Negatively-Charged Silicon-Vacancy Centers in Diamond
Journal-ref: Phys. Rev. Lett. 120, 117401 (2018)
Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)

Point defects in wide-bandgap semiconductors are emerging as versatile resources for nanoscale sensing and quantum information science but our understanding of the photo-ionization dynamics is presently incomplete. Here we use two-color confocal microscopy to investigate the dynamics of charge in Type 1b diamond hosting nitrogen-vacancy (NV) and silicon-vacancy (SiV) centers. By examining the non-local fluorescence patterns emerging from local laser excitation, we show that in the simultaneous presence of photo-generated electrons and holes, SiV (NV) centers selectively transform into the negative (neutral) charge state. Unlike NVs, 532 nm illumination ionizes SiV- via a single photon process thus hinting at a comparatively shallower ground state. In particular, slower ionization rates at longer wavelengths suggest the latter lies approximately ~1.9 eV below the conduction band minimum. Building on the above observations we demonstrate on-demand SiV and NV charge initialization over large areas via green laser illumination of variable intensity.

[33]  arXiv:1803.06570 [pdf, ps, other]
Title: Local Quantum Criticality of a One-Dimensional Kondo Insulator Model
Authors: W. Zhu, Jian-xin Zhu
Subjects: Strongly Correlated Electrons (cond-mat.str-el)

The continuous quantum phase transition and the nature of quantum critical point (QCP) in a modified Kondo lattice model with Ising anisotropic exchange interactions is studied within the density-matrix renormalization group algorithm. We investigate the effect of quantum fluctuations on critical Kondo destruction QCP, by probing static and dynamic properties of the magnetic order and the Kondo effect. In particular, we identify that local Kondo physics itself becomes critical at the magnetic phase transition point, providing unbiased evidences for local quantum criticality between two insulators without resorting to the change of Fermi surface.

[34]  arXiv:1803.06574 [pdf, other]
Title: Dynamical Localization in $\mathbb{Z}_2$ Lattice Gauge Theories
Comments: 19 pages (14 + appendices), 13 figures
Subjects: Strongly Correlated Electrons (cond-mat.str-el)

We study quantum quenches in two-dimensional lattice gauge theories with fermions coupled to dynamical $\mathbb{Z}_2$ gauge fields. Through the identification of an extensive set of conserved quantities, we propose a generic mechanism of charge localization in the absence of quenched disorder both in the Hamiltonian and in the initial states. We provide diagnostics of this localization through a set of experimentally relevant dynamical measures, entanglement measures, as well as spectral properties of the model. One of the defining features of the models which we study is a binary nature of emergent disorder, related to $\mathbb{Z}_2$ degrees of freedom. This results in a qualitatively different behaviour in the strong disorder limit compared to typically studied models of localization. For example it gives rise to a possibility of delocalization transition via a mechanism of quantum percolation in dimensions higher than 1D. We highlight the importance of our general phenomenology to questions related to dynamics of defects in Kitaev's toric code, and to quantum quenches in Hubbard models. While the simplest models we consider are effectively non-interacting, we also include interactions leading to many-body localization-like logarithmic entanglement growth. Finally, we consider effects of interactions which generate dynamics for conserved charges, which gives rise to only transient localization behaviour, or quasi-many-body-localization.

[35]  arXiv:1803.06575 [pdf, other]
Title: Dynamics of a Lattice Gauge Theory with Fermionic Matter -- Minimal Quantum Simulator with Time-Dependent Impurities in Ultracold Gases
Comments: 6 pages, 4 figures
Subjects: Quantum Gases (cond-mat.quant-gas); Strongly Correlated Electrons (cond-mat.str-el)

We propose a minimal cold atomic gas quantum simulator for studying the real-time dynamics of a $\mathbb{Z}_2$ lattice gauge theory minimally coupled to fermionic matter. Using duality transformations we show that dynamical correlators of the gauge field can be obtained by measuring the dynamics of two pairs of impurities in a lattice of free fermions. We provide a protocol for the implementation of this minimal setting in a cold atomic gas experiment and predict a number of unusual experimental features in the integrable limit of the gauge theory. Finally, we show how the experimental setting can easily be extended to non-integrable regimes for exploring strongly interacting gauge theories beyond the capabilities of classical computers.

[36]  arXiv:1803.06580 [pdf, other]
Title: Aging is a (log-)Poisson Process, not a Renewal Process
Authors: Stefan Boettcher, Dominic M. Robe (Emory U), Paolo Sibani (Syddansk U)
Comments: RevTex, 5 pages plus 3-page supplement, for related information, see this http URL
Subjects: Soft Condensed Matter (cond-mat.soft); Disordered Systems and Neural Networks (cond-mat.dis-nn); Materials Science (cond-mat.mtrl-sci)

Aging is a ubiquitous relaxation dynamic in disordered materials. It ensues after a rapid quench from an equilibrium "fluid" state into a non-equilibrium, history-dependent jammed state. We propose a physically motivated description that contrasts sharply with a continuous-time random walk (CTRW) with broadly distributed trapping times commonly used to fit aging data. A renewal process like CTRW proves irreconcilable with the log-Poisson statistic exhibited, for example, by jammed colloids as well as by disordered magnets. A log-Poisson process is characteristic of the intermittent and decelerating dynamics of jammed matter usually activated by record-breaking fluctuations ("quakes"). We show that such a record dynamics (RD) provides a universal model for aging, physically grounded in generic features of free-energy landscapes of disordered systems.

[37]  arXiv:1803.06593 [pdf]
Title: Bulk transport properties of Bismuth selenide thin films approaching the two-dimensional limit
Comments: 13 pages, 4 figures
Subjects: Materials Science (cond-mat.mtrl-sci)

We have investigated the transport properties of topological insulator Bi2Se3 thin films grown using magnetron sputtering with an emphasis on understanding the behavior as a function of thickness. We show that thickness has a strong influence on all aspects of transport as the two-dimensional limit is approached. Bulk resistivity and Hall mobility show disproportionately large changes below 6 quintuple layer which we directly correlate to an increase in the bulk band gap of few-layer Bi2Se3, an effect that is concomitant with surface gap opening. A tendency to crossover from a metallic to an insulating behavior in temperature-dependent resistivity measurements in ultra-thin Bi2Se3 is also consistent with an increase in the bulk band gap along with enhanced disorder at the film-substrate interface. Our work highlights that the properties of few-layer Bi2Se3 are tunable that may be attractive for a variety of device applications in areas such as optoelectronics, nanoelectronics and spintronics.

[38]  arXiv:1803.06595 [pdf]
Title: New Nanoporous Graphyne Monolayer as Nodal Line Semimetal: Double Dirac Points with an Ultrahigh Fermi Velocity
Comments: 22 pages,6 figures
Subjects: Materials Science (cond-mat.mtrl-sci)

Two-dimensional (2D) carbon materials play an important role in nanomaterials. We propose a new carbon monolayer, named hexagonal-4,4,4-graphyne (H4,4,4-graphyne), which is a nanoporous structure composed of rectangular carbon rings and triple bonds of carbon. Using first-principles calculations, we systematically studied the structure, stability, and band structure of this new material. We found that its energy is much lower than that of some experimental carbon materials and it is stable at least up to 1500 K. In contrast to the single Dirac point band structure of other 2D carbon monolayers, the band structure of H4,4,4-graphyne exhibits double Dirac points along the high symmetry points and the corresponding Fermi velocities (1.04~1.27 * 106 m/s) are asymmetric and higher than that of graphene. The origin of these double Dirac points is traced back to the nodal line states, which can be well explained by a tight-binding model. The H4,4,4-graphyne forms a moir\'e superstructure when placed on top of a BN substrate, while keeping the double Dirac points. These properties make H4,4,4-graphyne a promising semimetal material for applications in high-speed electronic devices.

[39]  arXiv:1803.06605 [pdf, ps, other]
Title: An experimental and Ab-initio study of Electronic and Magnetic properties of FeGa3
Comments: 9 figures, 1 table
Subjects: Materials Science (cond-mat.mtrl-sci)

Electronic structure of FeGa3 has been studied using experiments and ab-initio calculations. Magnetization measurements show that FeGa3 is inherently diamagnetic in nature. Our studies indicate that the previously reported magnetic moment on the Fe atoms in FeGa3 is not an intrinsic property of FeGa3, but is primarily due to the presence of disorder, defects, grain boundaries etc that break the symmetry about the Fe dimers. Analysis of the results obtained from magnetic measurements, photoelectron spectroscopy, Fe K-edge X-ray absorption near edge spectroscopy and ab-initio calculations clearly indicates that, the effects of on-site Coulomb repulsion between the Fe 3d electrons do not play any role in determining the electronic and magnetic properties of FeGa3. Detailed analysis of results of single crystal and poycrystalline FeGa3, helps to resolve the discrepancy in the electronic and magnetic properties in FeGa3 existing in the literature, consistently.

[40]  arXiv:1803.06606 [pdf, other]
Title: Stripes and honeycomb lattice of quantized vortices in rotating two-component Bose-Einstein condensates
Comments: 6 pages, 4 figures
Subjects: Quantum Gases (cond-mat.quant-gas)

We study numerically the structure of a vortex lattice in two-component Bose-Einstein condensates with equal atomic masses and equal intra- and inter-component coupling strengths. The numerical simulations of the Gross-Pitaevskii equation show that the quantized vortices form uncertain lattice configurations accompanying the vortex stripes, honeycomb lattices, and their complexes. This is a result of the degeneracy of the system for the SU(2) symmetric operation, which makes a continuous transformation between the above structures. In terms of the pseudospin representation, the complex lattice structures are identified to a hexagonal lattice of doubly-winding half-skyrmions.

[41]  arXiv:1803.06607 [pdf, other]
Title: Valley Hall Transport of Photon-Dressed Quasiparticles in 2D Dirac Semiconductors
Comments: 6 pages, 4 figures
Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)

We present a theory of the photovoltaic valley-dependent Hall effect in a two-dimensional Dirac semiconductor subject to an intense near-resonant electromagnetic field. Our theory captures and elucidates the influence of both the field-induced resonant interband transitions and the nonequilibrium carrier kinetics on the resulting valley Hall transport in terms of photon-dressed quasiparticles. The non-perturbative renormalization effect of the pump field manifests itself in the dynamics of the photon-dressed quasiparticles, with a quasienergy spectrum characterized by dynamical gaps $\delta_\eta$ ($\eta$ is the valley index) that strongly depend on field amplitude and polarization. Non-equilibrium carrier distribution functions are determined by the pump field frequency $\omega$ as well as the ratio of intraband relaxation time $\tau$ and interband recombination time $\tau_{\mathrm{rec}}$. We obtain analytic results in three regimes, when (I) all relaxation processes are negligible, (II) $\tau \ll \tau_{\mathrm{rec}}$, and (III) $\tau \gg \tau_{\mathrm{rec}}$, and display corresponding asymptotic dependences on $\delta_\eta$ and $\omega$. We then apply our theory to two-dimensional transition-metal dichalcogenides, and find a strong enhancement of valley-dependent Hall conductivity as the pump field frequency approaches the transition energies between the pair of spin-resolved conduction and valence bands at the two valleys.

[42]  arXiv:1803.06618 [pdf, ps, other]
Title: Simple mechanisms for magnetooscillations NOT to detect Berry phase
Comments: 7 pages, 4 figures
Subjects: Strongly Correlated Electrons (cond-mat.str-el); Mesoscale and Nanoscale Physics (cond-mat.mes-hall)

Phase of quantum magnetooscilalions is often associated with the Berry phase and is widely used to argue in favor of topological non-triviality of the system (Berry phase $2\pi n+\pi$). Nevertheless, the experimentally determined value may deviate from $2\pi n+\pi$ arbitrarily. In this paper we suggest two simple mechanisms drammatically affecting the experimentally observed value of the phase in three-dimensional topological insulators: (i) magnetic field dependence of the chemical potential, and (ii) possible non-uniformity of the system. These mechanisms are not limited to topological insulators and can be extended to other topologically trivial and non-trivial systems.

[43]  arXiv:1803.06619 [pdf]
Title: The impact of Hubbard- and van der Waals-corrections on the DFT calculation of epsilon-zeta transition pressure in solid oxygen
Comments: 4 pages, 4 figure
Subjects: Materials Science (cond-mat.mtrl-sci)

The aim of this study is to clarify the physics which governs the transition from epsilon phase to zeta phase of solid oxygen observed experimentally at 96 GPa using density functional theory (DFT). The transition was predicted at 40 GPa with PBE functional. Then the Hubbard correction was added to enhance the localization of p-orbital of oxygen. The epsilon-zeta transition pressure was significantly improved to 70 GPa. Finally, we included the non-local van der Waals correction. The transition pressure slightly increases to 80 GPa. These results demonstrate that the contribution from Hubbard term is superior to van der Waals term.

[44]  arXiv:1803.06654 [pdf, other]
Title: Inelastic scattering of microwave radiation in the Coulomb blockade: Microwave absorption, amplification, and squeezing by inelastic Cooper-pair tunneling
Comments: 18 pages, 6 figures
Subjects: Superconductivity (cond-mat.supr-con); Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Quantum Physics (quant-ph)

We study scattering of propagating microwave fields by a DC-voltage-biased Josephson junction. At sub-gap voltages, a small Josephson junction works merely as a non-linear boundary that can absorb, amplify, and diversely convert propagating microwaves. We find that in the leading-order perturbation theory of the Josephson coupling energy, the spectral density and quadrature fluctuations of scattered thermal and coherent radiation can be described in terms of the well-known $P(E)$ function. Applying this, we show how thermal and coherent radiation can be absorbed and amplified in a circuit with a resonance frequency. We also show when a coherent input can create a two-mode squeezed output. In addition, we evaluate scattering amplitudes between arbitrary photon-number (Fock) states, describing individual photon multiplication and absorption processes occuring at the junction.

[45]  arXiv:1803.06656 [pdf]
Title: Optical Property Study of Charge Compensated (Si, Na) Co-doped ZnO
Subjects: Materials Science (cond-mat.mtrl-sci)

ZnO is co-doped with Na+ and Si4+ in the ratio 2:1. The ratio was intentionally chosen so that net valence state of dopant theoretically matches that of host. This is to avoid dependence in the amount of oxygen vacancies/interstitials arising out of cationic valence state of the dopant. With such a combination, modifications in structural and optical properties do not depend on excess or deficit of the dopant charge state. For lower doping, Na+ ions behave as interstitial sites which enhance strain, lattice disorder and thereby creating defects. Formation of interstitial defects leads to reduction in bandgap energy and produce orange-red luminescence. For higher doping, Na+ starts substituting at Zn2+ site which helps in reducing strain and lattice disorder and thereby increases bandgap. Inspite of presence of Si4+ with higher charge, there is a gradual increase in oxygen vacancies due to lattice disorder.

[46]  arXiv:1803.06672 [pdf, ps, other]
Title: Topological phases and edge states in a non-Hermitian trimerized optical lattice
Authors: L. Jin
Comments: 9 pages, 7 figures
Journal-ref: Physical Review A 96, 032103 (2017)
Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Quantum Physics (quant-ph)

Topologically engineered optical materials support robust light transport. Herein, the investigated non-Hermitian lattice is trimerized and inhomogeneously coupled using uniform intracell coupling. The topological properties of the coupled waveguide lattice are evaluated, the PT-symmetric phase of a PT-symmetric lattice can have different topologies; the edge states depend on the lattice size, boundary configuration, and competition between the coupling and degree of non-Hermiticity. The topologically nontrivial region extends in the presence of periodic gain and loss. The nonzero geometric phases accumulated by the Bloch bands indicate the existence of topologically protected edge states between the band gaps. The unidirectional amplification and attenuation zero modes appear above a threshold degree of non-Hermiticity, which facilitate the development of a robust optical diode.

[47]  arXiv:1803.06682 [pdf, other]
Title: Supervised learning magnetic skyrmion phases
Subjects: Strongly Correlated Electrons (cond-mat.str-el); Disordered Systems and Neural Networks (cond-mat.dis-nn)

We propose a simple and transparent machine learning approach for recognition and classification of complex non-collinear magnetic structures in two-dimensional materials. It is based on the implementation of the single-hidden-layer neural network that only relies on the z projections of the spins. In this setup one needs a limited set of magnetic configurations to distiguish ferromagnetic, skyrmion and spin spiral phases, as well as their different combinations. The network trained on the configurations for square-lattice Heisenberg model with Dzyaloshinskii-Moriya interaction can classify the magnetic structures obtained from Monte Carlo calculations for triangular lattice. Our approach is also easy to use for analysis of the numerous experimental data collected with spin-polarized scanning tunneling experiments.

[48]  arXiv:1803.06709 [pdf, ps, other]
Title: p-wave superfluidity in mixtures of ultracold Fermi and spinor Bose gases
Comments: 6 pages, 2 figures
Subjects: Quantum Gases (cond-mat.quant-gas)

We reveal that the p-wave superfluid can be realized in a mixture of fermionic and F=1 bosonic gases. We derive a general set of the gap equations for gaps in the s- and p-channels. It is found that the spin-spin bose-fermi interactions favor the p-wave pairing and naturally suppress the pairing in the s-channel. The gap equations for the polar phase of p-wave superfluid fermions are numerically solved. It is shown that a pure p-wave superfluid can be observed in a well-controlled environment of atomic physics.

[49]  arXiv:1803.06726 [pdf, other]
Title: Theory of Orbital Magnetic Quadrupole Moment and Nonlinear Anomalous Thermoelectric Transport
Authors: Y. Gao, D. Xiao
Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)

We present a microscopic theory of the magnetic quadrupole moment density $\Qij$ in periodic crystals using the semiclassical framework of electron dynamics. We obtain a gauge-invariant expression with clear physical interpretation and demonstrate the typical behaviour of $\Qij$ in a minimal two-band model that hosts a tilted Dirac cone. We then show that $\Qij$ leads to an intrinsic nonlinear anomalous thermoelectric current. This effect can be used to probe systems with combined time reversal and inversion symmetry. As an example, we calculate the nonlinear Nernst and Hall current in the loop-current model for cuprate superconductors, and find they are greatly enhanced around Dirac points and saddle points of the energy band, respectively.

[50]  arXiv:1803.06736 [pdf, other]
Title: Effect of the gap anisotropy on the spin resonance peak in superconducting state of iron-based materials
Authors: M.M. Korshunov
Comments: 7 pages + 1 page supplementary materials
Subjects: Superconductivity (cond-mat.supr-con)

We study the spin resonance in the superconducting state of iron-based materials within the multiorbital model with unequal anisotropic gaps on different Fermi surface sheets. We show that the resonance peak shifts to higher frequencies with increasing the zero-amplitude gap magnitude. On the contrary, with increasing the gap anisotropy, it shifts to lower frequencies and lose some intensity.

[51]  arXiv:1803.06741 [pdf]
Title: Superconducting Magnetic Bearings Simulation using an H-formulation Finite Element Model
Comments: 22 pages, 15 figures
Subjects: Superconductivity (cond-mat.supr-con)

The modeling of superconducting magnetic bearing (SMB) is of great significance for predicting and optimizing its levitation performance before construction. Although lots of efforts have been made in this area, it still remains some space for improvements. Thus the goal of this work is to report a flexible, fast and trustworthy H-formulation finite element model. First the methodology for modeling and calibrating both bulk-type and stack-type SMB is summarized. Then its effectiveness for simulating SMBs in 2-D, 2-D axisymmetric and 3-D is evaluated by comparison with measurements. In particular, original solutions to overcome several obstacles are given: clarification of the calibration procedure for stack-type and bulk-type SMBs, details on the experimental protocol to obtain reproducible measurements, validation of the 2-D model for a stack-type SMB modeling the tapes real thickness, implementation of a 2-D axisymmetric SMB model, implementation of a 3-D SMB model, extensive validation of the models by comparison with experimental results for field cooling and zero field cooling, for both vertical and lateral movements. The accuracy of the model being proved, it has now a strong potential for speeding up the development of numerous applications including maglev vehicles, magnetic launchers, flywheel energy storage systems, motor bearings and cosmic microwave background polarimeters.

[52]  arXiv:1803.06743 [pdf, other]
Title: Raising the superconducting $T_\mathrm{c}$ of gallium: in-situ characterization of the transformation of $α$-Ga into $β$-Ga
Subjects: Superconductivity (cond-mat.supr-con)

Gallium (Ga) displays several metastable phases. Superconductivity is strongly enhanced in the metastable $\mathrm{\beta}$-Ga with a critical temperature $T_\mathrm{c}= 6.04(5)\,\mathrm{K}$, while stable $\mathrm{\alpha}$-Ga has a much lower $T_\mathrm{c}<1.2\,\mathrm{K}$. Here we use a membrane-based nanocalorimeter to initiate the transition from $\mathrm{\alpha}$-Ga to $\mathrm{\beta}$-Ga on demand, as well as study the specific heat of the two phases on one and the same sample. The in-situ transformation is initiated by bringing the temperature to about $10\,\mathrm{K}$ above the melting temperature of $\mathrm{\alpha}$-Ga. After such treatment, the liquid supercools down to $232\,\mathrm{K}$, where $\mathrm{\beta}$-Ga solidifies. We find that $\mathrm{\beta}$-Ga is a strong-coupling type-I superconductor with $\Delta(0)/k_\mathrm{B}T_\mathrm{c} =2.00(5)$ and a Sommerfeld coefficient $\gamma_\mathrm{n} = 1.53(4)\,\mathrm{mJ/molK^2}$, 2.55 times higher than that in the $\alpha$ phase. The results allow a detailed comparison of fundamental thermodynamic properties between the two phases.

[53]  arXiv:1803.06749 [pdf, other]
Title: Shape transitions in two-body systems: two-electron quantum dots in a magnetic field
Comments: 15 pages, 12 figures
Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)

We present a thorough analysis of the electron density distribution (shape) of two electrons, confined in the three-dimensional harmonic oscillator potential, as a function of the perpendicular magnetic field.Explicit algebraic expressions are derived in terms of the system's parameters and the magnetic field strength to trace the shape transformations in the ground and low-lying excited states. We found that the interplay of the classical and quantum properties lead to a quantum shape transition from a lateral to a vertical localization of electrons in low-lying excited states at relatively strong Coulomb interaction with alteration of the magnetic field. In contrast, in that regime in the ground states the electrons form always a ring type distribution in the lateral plane. The analytical results demonstrate a good agreement with quantum numerical results near the transition point and at high magnetic field.

[54]  arXiv:1803.06759 [pdf, ps, other]
Title: Universal trimers of one-dimensional bosons with two- and three-body attractions
Authors: Yusuke Nishida
Comments: 5 pages, 2 figures
Subjects: Quantum Gases (cond-mat.quant-gas)

When quantum particles are confined into lower dimensions, an effective three-body interaction inevitably arises and may cause significant consequences. Here we study bosons in one dimension with weak two-body and three-body interactions and predict the existence of two three-body bound states when both interactions are attractive. Their binding energies are universal functions of the two-body and three-body scattering lengths and have direct relevance to a broad range of quasi-one-dimensional systems realized with ultracold atoms.

[55]  arXiv:1803.06769 [pdf, other]
Title: High temperature magnetism and microstructure of semiconducting ferromagnetic alloy (GaSb)$_{1-x}$(MnSb)$_{x}$
Comments: 7 pages, 6 figures (total of 19 panels)
Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Materials Science (cond-mat.mtrl-sci)

We have studied the properties of relatively thick (about 120 nm) magnetic composite films grown by pulsed laser deposition method using (GaSb)$_{0.59}$(MnSb)$_{0.41}$ eutectic compound as a target for sputtering. For the studied films we have observed ferromagnetism and anomalous Hall effect above the room temperature, it manifests the presence of spin-polarized carriers. Electron microscopy, atomic and magnetic force microscopy results suggests that films under study have homogenous columnar structure in the bulk while MnSb inclusions accumulate near it's surface. This is in good agreement with high mobility values of charge carriers. Based on our data we conclude that room temperature magnetic and magnetotransport properties of the films are defined by MnSb inclusions.

[56]  arXiv:1803.06771 [pdf]
Title: Tuning phase-stability and short-range order through Al-doping in FeMnCoCrAlx (x <= 20 at.%) high entropy alloys
Comments: 24 pages, 8 figures
Subjects: Materials Science (cond-mat.mtrl-sci)

For FeMnCoCrAlx high-entropy alloys, we investigate the phase evolution with increasing Al-content (0 <= x <=20 at.%). From first-principles theory, the Al-doping transitions the alloy structurally from fcc to bcc separated by a narrow two-phase region (fcc+bcc), which is well supported by our experiments. We highlight the effect of Al-doping on the formation enthalpy and electronic structure of FeMnCoCrAlx alloys. As chemical short-range order (SRO) in multicomponent alloys indicates the nascent local order (and entropy changes), as well as expected low-temperature ordered behavior, we use thermodynamic linear-response to predict SRO and ordering instabilities and their phase transformation temperatures present in FeMnCoCrAlx. The predictions agree with our present and other reported experimental findings.

[57]  arXiv:1803.06780 [pdf]
Title: Giant photoinduced lattice distortion in oxygen-vacancy ordered SrCoO2.5 thin films
Comments: 15 pages, 3 figures, support material
Subjects: Materials Science (cond-mat.mtrl-sci)

Despite of the tremendous studies of oxygen vacancy formation and migration in determining the structural evolution and property optimization of multivalent transition metal oxides, few has focused on the transient dynamic behaviors in the oxygen vacancy enrichment system under non-equilibrium states. In this work, we performed multi-timescale ultrafast X-ray diffraction techniques to monitor the structural dynamics in the oxygen-vacancy ordered SrCoO2.5 thin films and observed an unanticipatedly giant lattice distortion. Time-resolved synchrotron X-ray diffraction measurements were applied in the SrCoO2.5 thin films upon excitation of different photon energies for the SrCoO2.5 films with the different thicknesses. The giant magnitude of photoinduced strain ({\Delta}c/c > 1 %) and its distinct correlation with the pump photon energy indicate an undoubtedly non-thermal origin of the photoinduced strain. The sub-picosecond resolution X-ray diffraction reveals that the formation and propagation of the coherent acoustic phonons and further elongates the maximum distortion in the magnitude by 1.4 times at early time points. We propose a plausible mechanism for the giant lattice distortion upon the 400-nm-laser photoexcitation that it is the p-d charge transfer induced the rearrangement of the tilted Co-O octahedral induces the giant c-axis elongation.

[58]  arXiv:1803.06789 [pdf]
Title: Clear variation of spin splitting by changing electron distribution at non-magnetic metal/Bi2O3 interfaces
Subjects: Materials Science (cond-mat.mtrl-sci)

Large spin splitting at Rashba interface, giving rise to strong spin-momentum locking, is essential for efficient spin-to-charge conversion. Recently, a Cu/Bismuth oxide (Bi2O3) interface has been found to exhibit an efficient spin-to-charge conversion similar to a Ag/Bi interface with large Rashba spin splitting. However, the guiding principle of designing the metal/oxide interface for the efficient conversion has not been clarified yet. Here we report strong non-magnetic (NM) material dependence of spin splitting at NM/Bi2O3 interfaces. We employed spin pumping technique to inject spin current into the interface and evaluated the magnitude of interfacial spin-to-charge conversion. We observed large modulation and sign change in conversion coefficient which corresponds to the variation of spin splitting. Our experimental results together with first-principles calculations indicate that such large variation is caused by material dependent electron distribution near the interface. The results suggest that control of interfacial electron distribution by tuning the difference in work function across the interface may be an effective way to tune the magnitude and sign of spin-to-charge conversion and Rashba parameter at interface.

[59]  arXiv:1803.06826 [pdf]
Title: Terahertz radiation by subpicosecond spin-polarized photocurrent originating from Dirac electrons in a Rashba-type polar semiconductor
Comments: 23 pages including Supplemental Materials
Subjects: Strongly Correlated Electrons (cond-mat.str-el)

The spin-splitting energy bands induced by the relativistic spin-orbit interaction in solids provide a new opportunity to manipulate the spin-polarized electrons on the sub-picosecond time scale. Here, we report one such example in a bulk Rashba-type polar semiconductor BiTeBr. Strong terahertz electromagnetic waves are emitted after the resonant excitation of the interband transition between the Rashba-type spin-splitting energy bands with a femtosecond laser pulse circularly polarized. The phase of the emitted terahertz waves is reversed by switching the circular polarization. This suggests that the observed terahertz radiation originates from the subpicosecond spin-polarized photocurrents, which are generated by the asymmetric depopulation of the Dirac state. Our result provides a new way for the current-induced terahertz radiation and its phase control by the circular polarization of incident light without external electric fields.

[60]  arXiv:1803.06829 [pdf, ps, other]
Title: Exact confirmation of 1D nonlinear fluctuating hydrodynamics for a two-species exclusion process
Comments: 6 pages, 3 figures
Subjects: Statistical Mechanics (cond-mat.stat-mech); Mathematical Physics (math-ph); Probability (math.PR)

We consider current statistics for a two species exclusion process of particles hopping in opposite directions on a one-dimensional lattice. We derive an exact formula for the Green's function as well as for a joint current distribution of the model, and study its long time behavior. For a step type initial condition, we show that the limiting distribution is a product of the Gaussian and the GUE Tracy-Widom distribution. This is the first analytic confirmation for a multi-component system of a prediction from the recently proposed non-linear fluctuating hydrodynamics for one dimensional systems.

[61]  arXiv:1803.06834 [pdf, other]
Title: Ground-state wavefunction of macroscopic electron systems
Authors: Peter Fulde
Comments: 29 pages, 3 figures
Subjects: Other Condensed Matter (cond-mat.other); Quantum Physics (quant-ph)

Wavefunctions for large electron numbers $N$ are plagued by the Exponential Wall Problem (EWP), i.e., an exponential increase in the dimensions of Hilbert space with $N$. Therefore they loose their meaning for macroscopic systems, a point stressed in particular by W. Kohn. The EWP has to be resolved in order to be able to perform electronic structure calculations, e.g., for solids. The origin of the EWP is the multiplicative property of wavefunctions when independent subsystems are considered. Therefore it can only be avoided when wavefunctions are formulated so that they are additive instead, in particular when matrix elements involving them are calculated. We describe how this is done for the ground state of a macroscopic electron system. Going over from a multiplicative to an additive quantity requires taking a logarithm. Here it implies going over from Hilbert space to the operator- or Liouville space with a metric based on cumulants. The operators which define the ground-state wavefunction generate fluctuations from a mean-field state. The latter does not suffer from an EWP and therefore may serve as a vacuum state. The fluctuations have to be {\it connected} like the ones caused by pair interactions in a classical gas when the free energy is calculated (Meyer's cluster expansion). This fixes the metric in Liouville space. The scheme presented here provides a solid basis for electronic structure calculations for the ground state of solids. In fact, its applicability has already been proven. We discuss also matrix product states, which have been applied to one-dimensional systems with results of high precision. Although these states are formulated in Hilbert space they are processed by using operators in Liouville space. We show that they fit into the general formalism described above.

[62]  arXiv:1803.06835 [pdf]
Title: Prediction of two-dimensional nodal-line semimetal in a carbon nitride covalent network
Subjects: Materials Science (cond-mat.mtrl-sci)

Carbon nitride compounds have emerged recently as a prominent member of 2D materials beyond graphene. The experimental realizations of 2D graphitic carbon nitride g-C$_3$N$_4$, nitrogenated holey grahpene C$_2$N, polyaniline C$_3$N have shown their promising potential in energy and environmental applications. In this work, we predict a new type of carbon nitride network with a C$_9$N$_4$ stoichiometry from first principle calculations. Unlike common C-N compounds and covalent organic frameworks (COFs), which are typically insulating, surprisingly C$_9$N$_4$ is found to be a 2D nodal-line semimetal (NLSM). The nodal line in C$_9$N$_4$ forms a closed ring centered at $\Gamma$ point, which originates from the pz orbitals of both C and N. The linear crossing happens right at Fermi level contributed by two sets of dispersive Kagome and Dirac bands, which is robust due to negligible spin-orbital-coupling (SOC) in C and N. Besides, it is revealed that the formation of nodal ring is of accidental band degeneracy in nature induced by the chemical potential difference of C and N, as validated by a single orbital tight-binding model, rather than protected by crystal in-plane mirror symmetry or band topology. Interestingly, a new structure of nodal line, i.e., nodal-cylinder, is found in momentum space for AA-stacking C$_9$N$_4$. Our results imply possible functionalization for a novel metal-free C-N covalent network with interesting semimetallic properties.

[63]  arXiv:1803.06857 [pdf, other]
Title: Anomalous heat equation in a system connected to thermal reservoirs
Comments: Main text: 5 pages. Supplementary: 9 page. 5 Figures
Subjects: Statistical Mechanics (cond-mat.stat-mech); Mathematical Physics (math-ph); Chaotic Dynamics (nlin.CD)

We study anomalous transport in a one-dimensional system with two conserved quantities in presence of thermal baths. In this system we derive exact expressions of the temperature profile and the two point correlations in steady state as well as in the non-stationary state where the later describes the relaxation to the steady state. In contrast to the Fourier heat equation in the diffusive case, here we show that the evolution of the temperature profile is governed by a non-local anomalous heat equation. We provide numerical verifications of our results.

[64]  arXiv:1803.06869 [pdf, other]
Title: Realistic Floquet semimetal with exotic topological linkages between arbitrarily many nodal loops
Comments: 5.5 pages of main text plus 8 pages of supplementary material, totally 9 figures. Comments welcome
Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)

Valence and conduction bands in nodal loop semimetals (NLSMs) touch along closed loops in momentum space. If such loops can proliferate and link intricately, NLSMs become exotic topological phases with unconventional topological characteristics and potentially peculiar transport properties. In conventional quantum materials or cold atom systems alike, such exotic phases necessarily require non-local hopping and are therefore intrinsically unrealistic. In this work, we show how this hurdle can be surmounted through an experimentally feasible periodic driving scheme. In particular, by tuning the period of a two-step periodic driving or some experimentally accessible parameters, we show how to generate arbitrarily many nodal loops that are linked with various levels of complexity. Furthermore, we propose to use both the Berry phase winding and the Alexander polynomial topological invariant to characterize the fascinating linkages among the nodal loops. This work thus presents a class of exotic Floquet topological phase that has hitherto not been proposed in any realistic setup.

[65]  arXiv:1803.06906 [pdf, ps, other]
Title: Understanding dynamics of looping of a long chain polymer in solution: Wilemski-Fixman Approach
Comments: arXiv admin note: text overlap with arXiv:1611.05235
Subjects: Soft Condensed Matter (cond-mat.soft); Other Condensed Matter (cond-mat.other)

We investigate theoretically the end-to-end looping time of a long chain polymer molecule immersed in a solvent. The dynamics of the end-to-end distance is governed by a Smoluchowski-like equation of a particle moving under the influence of a parabolic potential in presence of a Dirac delta sink of arbitrary strength and location. Using Wilemski-Fixman [ G. Wilemski and M. Fixman, J. Chem. Phys. {\bf 60}, {\it 866} (1974)] approach we calculate the looping time for a long chain molecule immersed in a solvent. We find that looping time varies with several parameters such as length of the polymer (N), bond length (b) and the relaxation time ${\tau_R}$.

[66]  arXiv:1803.06912 [pdf]
Title: Non-linear double-peeling: experimental vs. theoretical predictions
Comments: 14 pages, 8 figures
Journal-ref: The Journal of Adhesion, 94 (1), 46-57, 2018
Subjects: Soft Condensed Matter (cond-mat.soft)

The double peeling of detachment of non-linear adhesive tapes from a flat Poly(methylmethacrylate) (PMMA) surface has been investigated from both experimental and theoretical point of view. Double peeling tests show that, as the detachment process advances, the peeling angle stabilizes on a limiting value {\theta}lim corresponding to a critical pull-off force Fc above which the tape is completely detached from the substrate. This observed behavior is in good agreement with results obtained following the new theory of multiple peeling and taking into account the hardening-softening non-linear behavior of the experimentally tested adhesive tapes and clarifies some aspects of the experimental data. In particular, the theoretical model shows that the value of the limiting peeling angle depends on the geometry of the adhesive tape as well as on the stiffness properties and on the interfacial energy {\Delta}{\gamma}. Finally, theoretical predictions confirm that solutions with a peeling angle lower than {\theta}lim are unstable.

[67]  arXiv:1803.06923 [pdf, ps, other]
Title: Spontaneous symmetry breaking and Higgs mode: comparing Gross-Pitaevskii and nonlinear Klein-Gordon equations
Comments: 11 pages, 0 figures, to be published in the open-access journal Symmetry, special issue "Broken Symmetry" (guest editor B.A. Molomed)
Subjects: Quantum Gases (cond-mat.quant-gas)

We discuss the mechanism of spontaneous symmetry breaking and the elementary excitations for a weakly-interacting Bose gas at finite temperature. We consider both the non-relativistic case, described by the Gross-Pitaevskii equation, and the relativistic one, described by the cubic nonlinear Klein-Gordon equation. We analyze similarities and differences in the two equations and, in particular, in the phase and amplitude modes (i.e. Goldstone and Higgs modes) of the bosonic matter field. We show that the coupling between phase and amplitude modes gives rise to a single gapless Bogoliubov spectrum in the non-relativistic case. Instead, in the relativistic case the spectrum has two branches: one is gapless and the other is gapped. In the non-relativistic limit we find that the relativistic spectrum reduces to the Bogoliubov one. Finally, as an application of the above analysis, we consider the Bose-Hubbard model close to the superfluid-Mott quantum phase transition and we investigate the elementary excitations of its effective action, which contains both non-relativistic and relativistic terms.

[68]  arXiv:1803.06937 [pdf, ps, other]
Title: Pearson's correlation coefficient in the theory of networks: A comment
Comments: one page
Subjects: Disordered Systems and Neural Networks (cond-mat.dis-nn); Social and Information Networks (cs.SI)

In statistics, the Pearson correlation coefficient $r_{x,y}$ determines the degree of linear correlation between two variables and it is known that $-1 \le r_{x,y} \le 1$. In the theory of networks, an interesting expression proposed in [PRL {\bf 89} 208701 (2002)] for degree-degree correlation coefficient $r_{j,k}$ has been in use. We prove that the suggested expression is incorrect overall and one should rather use the conventional form.

[69]  arXiv:1803.06939 [pdf, other]
Title: Motion of vortices in ferromagnetic spin-1 BEC
Authors: E.B. Sonin
Comments: 19 pages, 2 figures, to be published in the special issue of Fizika Nizkikh Temperatur dedicated to A.M.Kosevich. arXiv admin note: substantial text overlap with arXiv:1801.01099
Subjects: Other Condensed Matter (cond-mat.other)

The paper investigates dynamics of nonsingular vortices in a ferromagnetic spin-1 BEC, where spin and mass superfluidity coexist in the presence of uniaxial anisotropy (linear and quadratic Zeeman effect). The analysis is based on hydrodynamics following from the Gross-Pitaevskii theory. Cores of nonsingular vortices are skyrmions with charge, which is tuned by uniaxial anisotropy and can have any fractal value between 0 and 1. There are circulations of mass and spin currents around these vortices. The results are compared with the equation of vortex motion derived earlier in the Landau-Lifshitz-Gilbert theory for magnetic vortices in easy-plane ferromagnetic insulators. In the both cases the transverse gyrotropic force (analog of the Magnus force in superfluid and classical hydrodynamics) is proportional to the charge of skyrmions in vortex cores.

[70]  arXiv:1803.06941 [pdf, ps, other]
Title: Oscillations of magnetization in topological line-node semimetals
Comments: 7 pages, 4 figures. arXiv admin note: text overlap with arXiv:1712.04300
Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Materials Science (cond-mat.mtrl-sci)

We theoretically investigate the phase of the de Haas - van Alphen oscillations in topological line-node semimetals. In these semimetals the chemical potential of charge carriers can essentially depend on the magnetic field, and this dependence changes the phase of the oscillations as compared to the phase in a three-dimensional metal with a band-contact line. Our results elucidate recent experimental data on the Berry phase for certain electron orbits in ZrSiS, ZrSiTe, and ZrSiSe.

[71]  arXiv:1803.06945 [pdf, other]
Title: Spin-orbital-lattice entangled states in cubic $d^1$ double perovskites
Comments: 6+5 pages, 7 figures
Subjects: Strongly Correlated Electrons (cond-mat.str-el)

Interplay of spin-orbit coupling and vibronic coupling on heavy $d^1$ site of cubic double perovskites is investigated by ab initio calculations. The stabilization energy of spin-orbital-lattice entangled states is found comparable to or larger than the exchange interactions, suggesting the presence of Jahn-Teller dynamics in the systems. In Ba$_2$YMoO$_6$, the pseudo JT coupling enhances the mixing of the ground and excited spin-orbit multiplet states, which results in strong temperature dependence of effective magnetic moments. The entanglement of the spin and lattice degrees of freedom induces a strong magneto-elastic response. This multiferroic effect is at the origin of the recently reported breaking of local point symmetry accompanying the development of magnetic ordering in Ba$_2$NaOsO$_6$.

[72]  arXiv:1803.06957 [pdf, other]
Title: Quenched dynamics and spin-charge separation in an interacting topological lattice
Comments: 5 pages 3 figures + 2 pages 2 figures
Subjects: Quantum Gases (cond-mat.quant-gas); Strongly Correlated Electrons (cond-mat.str-el); Quantum Physics (quant-ph)

We analyze the static and dynamical properties of a one-dimensional topological lattice, the fermionic Su-Schrieffer-Heeger model, in the presence of on-site interactions. Based on a study of charge and spin correlation functions, we elucidate the nature of the topological edge modes, which depending on the sign of the interactions, either display particles of opposite spin on opposite edges, or a pair and a holon. This study of correlation functions also highlights the strong entanglement that exists between the opposite edges of the system. This last feature has remarkable consequences upon subjecting the system to a quench, where an instantaneous edge-to-edge signal appears in the correlation functions characterizing the edge modes. Besides, other correlation functions are shown to propagate in the bulk according to the light-cone imposed by the Lieb-Robinson bound. Our study reveals how one-dimensional lattices exhibiting entangled topological edge modes allow for a non-trivial correlation spreading, while providing an accessible platform to detect spin-charge separation using state-of-the-art experimental techniques.

[73]  arXiv:1803.06961 [pdf]
Title: Enhanced spin-orbit torque via interface engineering in Pt/CoFeB/MgO heterostructures
Subjects: Materials Science (cond-mat.mtrl-sci)

Spin-orbit torque facilitates efficient magnetization switching via an in-plane current in perpendicularly magnetized heavy metal/ferromagnet heterostructures. The efficiency of spin-orbit-torque-induced switching is determined by the charge-to-spin conversion arising from either bulk or interfacial spin-orbit interactions, or both. Here, we demonstrate that the spin-orbit torque and the resultant switching efficiency in Pt/CoFeB systems are significantly enhanced by an interfacial modification involving Ti insertion between the Pt and CoFeB layers. Spin pumping and X-ray magnetic circular dichroism experiments reveal that this enhancement is due to an additional interface-generated spin current of the nonmagnetic interface and/or improved spin transparency achieved by suppressing the proximity-induced moment in the Pt layer. Our results demonstrate that interface engineering affords an effective approach to improve spin-orbit torque and thereby magnetization switching efficiency.

[74]  arXiv:1803.06993 [pdf, other]
Title: Superconductivity at low density near a ferroelectric quantum critical point: doped SrTiO
Comments: 7 pages, 2 figs
Subjects: Superconductivity (cond-mat.supr-con); Strongly Correlated Electrons (cond-mat.str-el)

Recent experiments on electron- or hole-doped SrTiO$_{3}$ have revealed a hitherto unknown form of superconductivity, where the Fermi energy of the paired electrons is much lower than the energies of the bosonic excitations thought to be responsible for the attractive interaction. We show that this situation requires a fully dynamical treatment of the problem calling for (i) a systematic modeling of the dynamical screening of the Coulomb interaction by ionic and electronic charges and (ii) a transverse optical phonon mediated pair interaction. The model allows for a nearly parameter free calculation of the transition temperature as a function of both, the doping concentration and the dielectric properties of the host system. The additional interaction mediated by the transverse optical soft phonon is shown to be essential in explaining the observed anomalous isotope effect. The model allows to capture the effect of the incipient (or real) ferroelectric phase in pure, or oxygen isotope substituted SrTiO$_{3}$

[75]  arXiv:1803.06998 [pdf, other]
Title: Activation of carbon doped hexagonal boron nitride: A mechanistic view from first-principles in the light of oxygen reduction and evolution
Comments: 9 pages, 7 figures
Subjects: Materials Science (cond-mat.mtrl-sci)

Electro-chemical fuel-cells are promising as environmentally sustainable non-fossil source of energy. A key reason for their limited application is the cost of their catalytic electrodes made of precious metals. Calibrated activation required for optimal catalysis makes it difficult to find alternates. Juxtaposed to the boron(B) and/or nitrogen(N) doped graphene proposed in recent years, we propose from first principles computation, super-lattices of graphene patches embedded in hexagonal boron-nitride(h-BN) as alternates, which can be more robust, hard and resilient than graphene. Our proposal is based on extensive atomistic study of realistic scenarios of substitution by carbon(C) in h-BN and chemical activation thereof, which brings out the fundamental role of Coulomb correlation between electrons of opposite spins in determining the chemistry of bipartite systems. The perceived lack of in-plane transferability of charge due to the insulating nature of h-BN is shown to be surmountable through formation of half-metallic honeycomb-Kagome super-lattices of active graphene patches.

[76]  arXiv:1803.07003 [pdf, other]
Title: Efficient algorithm to compute the second Chern number in four dimensional systems
Comments: 11 pages, 4 color figures
Subjects: Quantum Gases (cond-mat.quant-gas); Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Strongly Correlated Electrons (cond-mat.str-el); Quantum Physics (quant-ph)

Topological insulators are exotic material that possess conducting surface states protected by the topology of the system. They can be classified in terms of their properties under discrete symmetries and are characterized by topological invariants. The latter has been measured experimentally for several models in one, two and three dimensions in both condensed matter and quantum simulation platforms. The recent progress in quantum simulation opens the road to the simulation of higher dimensional Hamiltonians and in particular of the 4D quantum Hall effect. These systems are characterized by the second Chern number, a topological invariant that appears in the quantization of the transverse conductivity for the non-linear response to both external magnetic and electric fields. This quantity cannot always be computed analytically and there is therefore a need of an algorithm to compute it numerically. In this work, we propose an efficient algorithm to compute the second Chern number in 4D systems. We construct the algorithm with the help of lattice gauge theory and discuss the convergence to the continuous gauge theory. We benchmark the algorithm on several relevant models, including the 4D Dirac Hamiltonian and the 4D quantum Hall effect and verify numerically its rapid convergence.

[77]  arXiv:1803.07010 [pdf, other]
Title: Diffusion and first-passage characteristics on a dynamically evolving support
Comments: 9 pages, 5 figures
Subjects: Statistical Mechanics (cond-mat.stat-mech)

We propose a generalized diffusion equation for a flat Euclidean space subjected to a continuous infinitesimal scale transform. For the special cases of an algebraic or exponential expansion/contraction, governed by time-dependent scale factors $a(t)\sim t^\lambda$ and $a(t)\sim \exp(\mu t)$, the partial differential equation is solved analytically and the asymptotic scaling behavior, as well as the dynamical exponents, are derived. Whereas in the algebraic case the two processes (diffusion and expansion) compete and a crossover is observed, we find that for exponential dynamics the expansion dominates on all time scales. For the case of contracting spaces, an algebraic evolution slows down the overall dynamics, reflected in terms of a new effective diffusion constant, whereas an exponential contraction neutralizes the diffusive behavior entirely and leads to a stationary state. Furthermore, we derive various first-passage properties and describe four qualitatively different regimes of (strong) recurrent/transient behavior depending on the scale factor exponent.

[78]  arXiv:1803.07019 [pdf]
Title: Observation of Nuclear Quantum Effects and Hydrogen Bond Symmetrisation in High Pressure Ice
Subjects: Materials Science (cond-mat.mtrl-sci)

Hydrogen bond symmetrisations in H-bonded systems triggered by pressure induced nuclear quantum effects (NQEs) is a long-known concept1 but experimental evidences in high-pressure ices have remained elusive with conventional methods2,3. Theoretical works predicted quantum-mechanical tunneling of protons within water ices to occur at pressures above 30 GPa and the H-bond symmetrisation transition above 60 GPa4. Here, we used 1H-NMR on high-pressure ice up to 90 GPa, and demonstrate that NQEs govern the behavior of the hydrogen bonded protons in ice VII already at significantly lower pressures than previously expected. A pronounced tunneling mode was found to be present up to the highest pressures of 90 GPa, well into the stability field of ice X, where NQEs are not anticipated in a fully symmetrized H-bond network. We found two distinct transitions in the NMR shift data at about 20 GPa and 75 GPa attributed to the step-wise symmetrization of the H-bond (HB), with high-barrier H-Bonds (HBHB) to low-barrier H-bonds (LBHB) and LBHB to symmetric H-bonds (SHB) respectively. These transitions could have major implication on the physical properties of high-pressure ices and planetary interior models. NQEs observed in this chemically simple system over a wide pressure range could prove to be useful in designing a new generation of electronic devices exploiting protonic tunneling.

[79]  arXiv:1803.07025 [pdf]
Title: Evidence from EXAFS for Different Ta/Ti Site Occupancy in High Critical Current Density Nb$_3$Sn Superconductor Wires
Comments: 14 pages, 6 figures
Journal-ref: Scientific Reports 8, 4798 (2018)
Subjects: Superconductivity (cond-mat.supr-con)

To meet critical current density, J$_c$, targets for the Future Circular Collider (FCC), the planned replacement for the Large Hadron Collider (LHC), the high field performance of Nb$_3$Sn must be improved, but champion J$_c$ values have remained static for the last 10 years. Making the A15 phase stoichiometric and enhancing the upper critical field H$_{c2}$ by Ti or Ta dopants are the standard strategies for enhancing high field performance but detailed recent studies show that even the best modern wires have broad composition ranges. To assess whether further improvement might be possible, we employed EXAFS to determine the lattice site location of dopants in modern high-performance Nb$_3$Sn strands with J$_c$ values amongst the best so far achieved. Although Ti and Ta primarily occupy the Nb sites in the A15 structure, we also find significant Ta occupancy on the Sn site. These findings indicate that the best performing Ti-doped stand is strongly sub-stoichiometric in Sn and that antisite disorder likely explains its high average H$_{c2}$ behavior. These new results suggest an important role for dopant and antisite disorder in minimizing superconducting property distributions and maximizing high field J$_c$ properties.

[80]  arXiv:1803.07026 [pdf, other]
Title: New superexchange paths due to breathing-enhanced hopping in corner-sharing cuprates
Subjects: Strongly Correlated Electrons (cond-mat.str-el)

We present ab initio calculations of the superexchange antiferromagnetic spin coupling $J$ for two cuprates, Sr$_2$CuO$_3$ and La$_2$CuO$_4$. Good agreement with experimental estimates is obtained. We find that $J$ increases substantially as the distance between Cu and apical O is increased. There is an important synergetic effect of the Coulomb interaction, expanding the Cu $3d$ orbital when an electron hops into this orbital, and the O-Cu hopping, being increased by this orbital expansion (breathing). This is a new ingredient in superexchange models. In a model with a fixed basis, breathing effects can be described as a mixing of $3d$ and $4d$ orbitals or as a single $3d \to 4d$ excitation.

[81]  arXiv:1803.07047 [pdf, other]
Title: Electromagnetic response of quantum Hall systems in dimensions five and six and beyond
Comments: 18 pages, 4 figures
Subjects: Strongly Correlated Electrons (cond-mat.str-el); Applied Physics (physics.app-ph)

Quantum Hall (QH) states are arguably the most ubiquitous examples of nontrivial topological order, requiring no special symmetry and elegantly characterized by the first Chern number. Their higher dimension generalizations are particularly interesting from both mathematical and phenomenological perspectives, and have attracted recent attention due to a few high profile experimental realizations. In this work, we derive from first principles the electromagnetic response of QH systems in arbitrary number of dimensions, and elaborate on the crucial roles played by their modified phase space density of states under the simultaneous presence of magnetic field and Berry curvature. Besides providing new mathematical results relating this phase space modification to the non-commutativity of phase space, we also show how it produces a non-topological response current at leading order, in addition to the well-known topological contributions. This unconventional response appear only in five, six or more dimensions, and can be directly investigated through a few minimal models with specially chosen fluxes. These models, together with more generic 6D QH systems, can be realized in realistic 3D experimental setups like cold atom systems through possibly entangled synthetic dimensions.

[82]  arXiv:1803.07050 [pdf, other]
Title: Minimal dissipation in processes far from equilibrium
Comments: 5 pages, 4 figures, suppl. mater.: 3 pages, 4 figures
Subjects: Statistical Mechanics (cond-mat.stat-mech)

A central goal of thermodynamics is to identify optimal processes during which the least amount of energy is dissipated into the environment. Generally, even for simple systems, such as the parametric harmonic oscillator, optimal control strategies are mathematically involved, and contain peculiar and counter-intuitive features. We show that optimal driving protocols determined by means of linear response theory exhibit the same step and $\delta$-peak like structures that were previously found from solving the full optimal control problem. However, our method is significantly less involved, since only a minimum of a quadratic form has to be determined. In addition, our findings suggest that optimal protocols from linear response theory are applicable far outside their actual range of validity.

[83]  arXiv:1803.07059 [pdf, other]
Title: Autonomous Scanning Probe Microscopy in-situ Tip Conditioning through Machine Learning
Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)

Atomic scale characterization and manipulation with scanning probe microscopy rely upon the use of an atomically sharp probe. Here we present automated methods based on machine learning to automatically detect and recondition the quality of the probe of a scanning tunneling microscope. As a model system, we employ these techniques on the technologically relevant hydrogen-terminated silicon surface, training the network to recognize abnormalities in the appearance of surface dangling bonds. Of the machine learning methods tested a convolutional neural network yielded the greatest accuracy, achieving a positive identification of degraded tips in 97% of the test cases. By using multiple points of comparison and majority voting the accuracy of the method is improved beyond 99%. The methods described here can easily be generalized to other material systems and nanoscale imaging techniques.

[84]  arXiv:1803.07060 [pdf, other]
Title: Emergent geometric frustration and flat band in moiré bilayer graphene
Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Strongly Correlated Electrons (cond-mat.str-el)

So far the physics of moir\'e graphene bilayers at large, incommensurate rotation angles has been considered uninteresting. It has been held that the interlayer coupling in such structures is weak and the system can be thought of as a pair of decoupled single graphene sheets to a good approximation. Here, we demonstrate that for large rotation angles near commensurate ones, the interlayer coupling, far from being weak, is able to completely localize electrons to within a large scale, geometrically frustrated network of topologically protected modes. The emergent geometric frustration of the system gives rise to completely flat bands, with strong correlation physics as a result. All of this arises although in the lattice structure no large scale pattern appears to the unguided eye. Sufficiently close to commensuration the low-energy physics of this remarkable system has an exact analytical solution.

[85]  arXiv:1803.07061 [pdf, other]
Title: Coupling of magnetic order and charge transport in the candidate Dirac semimetal EuCd$_2$As$_2$
Comments: Supplemental information attached to preprint
Subjects: Strongly Correlated Electrons (cond-mat.str-el)

EuCd$_2$As$_2$ is a magnetic semimetal with unusual transport properties. It features similar networks of edge-sharing CdAs$_4$ tetrahedra to those found in the bulk Dirac semimetal Cd$_3$As$_2$, but in a layered, rather than three-dimensional, geometry and with interleaved planes of magnetic Eu$^{2+}$ ions. Here we use resonant elastic x-ray scattering to determine the evolution of magnetic order in EuCd$_2$As$_2$ below $T_\textrm{N}=9.5\,\textrm{K}$, as a function of temperature and applied magnetic field. We find an A-type antiferromagnetic structure with in-plane magnetic moments, and we observe dramatic magnetoresistive effects associated with field-induced changes in the magnetic structure and domain populations. Our ab initio electronic structure calculations indicate that the Dirac dispersion found in Cd$_3$As$_2$ is also present in EuCd$_2$As$_2$, but is gapped for $T < T_\textrm{N}$ due to the breaking of $C_3$ symmetry by the magnetic structure.

Cross-lists for Tue, 20 Mar 18

[86]  arXiv:1803.05333 (cross-list from physics.atm-clus) [pdf, ps, other]
Title: Observability of the Efimov spectrum in an electron-atom-atom system
Subjects: Atomic and Molecular Clusters (physics.atm-clus); Quantum Gases (cond-mat.quant-gas); Atomic Physics (physics.atom-ph)

The bound states of a system consisting of two heavy identical atoms and one light electron interacting through the finite-range pairwise potentials are explored, focusing on their dependence on the electron-atom scattering length. In the case of an exact resonance in the electron-atom interaction, the binding energy of an electron yields an effective $1/r^{2}$ potential for the relative motion of the atoms; One major finding is a universal potential that depends on the polarization length which goes beyond the Efimov region. An analytic expression for that potential is extracted from numerical calculations. The spectrum of the e+Rb+Rb system produced by the electron-atom polarization interaction exhibits three main sections, a non-universal transition region, a quasi-Efimov region, and a densely packed Efimov region.

[87]  arXiv:1803.06493 (cross-list from physics.bio-ph) [pdf, ps, other]
Title: Actin filaments growing against an elastic membrane: Effect of membrane tension
Comments: 16 pages, 13 figures
Journal-ref: Physical Review E, vol. 97, 032408 (2018)
Subjects: Biological Physics (physics.bio-ph); Soft Condensed Matter (cond-mat.soft); Statistical Mechanics (cond-mat.stat-mech)

We study the force generation by a set of parallel actin filaments growing against an elastic membrane. The elastic membrane tries to stay flat and any deformation from this flat state, either caused by thermal fluctuations or due to protrusive polymerization force exerted by the filaments, costs energy. We study two lattice models to describe the membrane dynamics. In one case, the energy cost is assumed to be proportional to the absolute magnitude of the height gradient (gradient model) and in the other case it is proportional to the square of the height gradient (Gaussian model). For the gradient model we find that the membrane velocity is a non-monotonic function of the elastic constant $\mu$, and reaches a peak at $\mu=\mu^\ast$. For $\mu < \mu^\ast$ the system fails to reach a steady state and the membrane energy keeps increasing with time. For the Gaussian model, the system always reaches a steady state and the membrane velocity decreases monotonically with the elastic constant $\nu$ for all nonzero values of $\nu$. Multiple filaments give rise to protrusions at different regions of the membrane and the elasticity of the membrane induces an effective attraction between the two protrusions in the Gaussian model which causes the protrusions to merge and a single wide protrusion is present in the system. In both the models, the relative time-scale between the membrane and filament dynamics plays an important role in deciding whether the shape of elasticity-velocity curve is concave or convex. Our numerical simulations agree reasonably well with our analytical calculations.

[88]  arXiv:1803.06526 (cross-list from physics.app-ph) [pdf]
Title: Titanium diboride ceramics for solar thermal absorbers
Journal-ref: Solar Energy Materials and Solar Cells, Volume 169 (2017) Pages 313-319
Subjects: Applied Physics (physics.app-ph); Materials Science (cond-mat.mtrl-sci)

Titanium diboride (TiB2) is a low-density refractory material belonging to the family of ultra-high temperature ceramics (UHTCs). This paper reports on the production and microstructural and optical characterization of nearly fully dense TiB2, with particular interest to its potential utilization as novel thermal solar absorber. Monolithic bulk samples are produced starting from elemental reactants by a two-step method consisting of the Self-propagating High-temperature Synthesis (SHS) followed by the Spark Plasma Sintering (SPS) of the resulting powders. The surface of obtained samples has-been characterized from the microstructural and topological points of view. The hemispherical reflectance spectrum has been measured from 0.3 to 15 um wavelength, to evaluate the potential of this material as solar absorber for future concentrating solar plants.

[89]  arXiv:1803.06546 (cross-list from physics.app-ph) [pdf, other]
Title: Microscale resolution thermal mapping using a flexible platform of patterned quantum sensors
Comments: 15 pages, 4 figures
Subjects: Applied Physics (physics.app-ph); Mesoscale and Nanoscale Physics (cond-mat.mes-hall)

Temperature sensors with micro- and nanoscale spatial resolution have long been explored for their potential to investigate the details of physical systems at an unprecedented scale. In particular, the rapid miniaturization of transistor technology, with the associated steep boost in power density, calls for sensors that accurately monitor heating distributions. Here, we report on a simple and scalable fabrication approach, based on directed self-assembly and transfer printing techniques, to construct arrays of nanodiamonds containing temperature sensitive fluorescent spin defects. The nanoparticles are embedded within a low thermal conductivity matrix that allows for repeated use on a wide range of systems with minimal spurious effects. Additionally, we demonstrate access to a wide spectrum of array parameters ranging from sparser single particle arrays to denser devices with approximately 100 % yield and stronger photoluminescence signal, ideal for temperature measurements. With these we experimentally reconstruct the temperature map of an operating coplanar waveguide to confirm the accuracy of these platforms.

[90]  arXiv:1803.06548 (cross-list from quant-ph) [pdf, ps, other]
Title: Perpetual emulation threshold of PT-symmetric Hamiltonians
Comments: 15 pages, 8 figures
Subjects: Quantum Physics (quant-ph); Quantum Gases (cond-mat.quant-gas)

We describe a technique to emulate a two-level \PT-symmetric spin Hamiltonian, replete with gain and loss, using only the unitary dynamics of a larger quantum system. This we achieve by embedding the two-level system in question in a subspace of a four-level Hamiltonian. Using an \textit{amplitude recycling} scheme that couples the levels exterior to the \PT-symmetric subspace, we show that it is possible to emulate the desired behaviour of the \PT-symmetric Hamiltonian without depleting the exterior, reservoir levels. We are thus able to extend the emulation time indefinitely, despite the non-unitary \PT dynamics. We propose a realistic experimental implementation using dynamically decoupled magnetic sublevels of ultracold atoms.

[91]  arXiv:1803.06599 (cross-list from quant-ph) [pdf, other]
Title: Single-Photon-Triggered Quantum Phase Transition
Comments: 7 pages, 5 figures, the initial submitted time (to journal) April 24, 2017
Subjects: Quantum Physics (quant-ph); Statistical Mechanics (cond-mat.stat-mech)

We propose a hybrid quantum model combining cavity QED and optomechanics, which allows the occurrence of equilibrium superradiant quantum phase transition (QPT) triggered by a single photon. This single-photon-triggered QPT exists both in the cases of ignoring and including the so-called $A^2$ term, i.e., it is immune to the no-go theorem. It originally comes from the photon-dependent quantum criticality featured by the proposed hybrid quantum model. Moreover, a reversed superradiant QPT is induced by the competition between the introduced $A^2$ term and the optomechanical interaction. This work offers an approach to manipulate QPT with a single photon, which should inspire the exploration of single-photon quantum-criticality physics and the engineering of new single-photon quantum devices.

[92]  arXiv:1803.06631 (cross-list from math-ph) [pdf, other]
Title: A Deal with the Devil: From Divergent Perturbation Theory to an Exponentially-Convergent Self-Consistent Expansion
Comments: 37 pages, 11 figures
Subjects: Mathematical Physics (math-ph); Statistical Mechanics (cond-mat.stat-mech)

For many nonlinear physical systems, approximate solutions are pursued by conventional perturbation theory in powers of the non-linear terms. Unfortunately, this often produces divergent asymptotic series, collectively dismissed by Abel as "an invention of the devil." An alternative method, the self-consistent expansion, has been introduced by Schwartz and Edwards. Its basic idea is a rescaling of the zeroth-order system around which the solution is expanded, to achieve optimal results. While low-order self-consistent calculations have been remarkably successful in describing the dynamics of non-equilibrium many-body systems (e.g., the Kardar-Parisi-Zhang equation), its convergence properties have not been elucidated before. To address this issue we apply this technique to the canonical partition function of the classical harmonic oscillator with a quartic $gx^{4}$ anharmonicity, for which perturbation theory's divergence is well-known. We explicitly obtain the $N^{\text{th}}$ order self-consistent expansion for the partition function, which is rigorously found to converge exponentially fast in $N$, and uniformly in $g$, for any coupling $g>0$. Comparing the self-consistent expansion with other methods that improve upon perturbation theory (Borel resummation, hyperasymptotics, Pad\'e approximants, and the Lanczos $\tau$-method), it compares favorably with all of them for small $g$ and dominates over them for large $g$. Remarkably, the self-consistent expansion is shown to successfully capture the correct partition function for the double-well potential case, where no perturbative expansion exists. Our treatment is generalized to the case of many oscillators, as well as to a more general nonlinearity of the form $g|x|^{q}$ with $q\ge0$ and complex $g$. These results allow us to treat the Airy function, and to see the fingerprints of Stokes lines in the self-consistent expansion.

[93]  arXiv:1803.06638 (cross-list from physics.data-an) [pdf, ps, other]
Title: Adaptive prior probabilities via optimization of risk and entropy
Comments: 15 pages, 3 figures
Subjects: Data Analysis, Statistics and Probability (physics.data-an); Statistical Mechanics (cond-mat.stat-mech); Computer Science and Game Theory (cs.GT)

An agent choosing between various actions tends to take the one with the lowest loss. But this choice is arguably too rigid (not adaptive) to be useful in complex situations, e.g. where exploration-exploitation trade-off is relevant, or in creative task solving. Here we study an agent that -- given a certain average utility invested into adaptation -- chooses his actions via probabilities obtained through optimizing the entropy. As we argue, entropy minimization corresponds to a risk-averse agent, whereas a risk-seeking agent will maximize the entropy. The entropy minimization can (under certain conditions) recover the epsilon-greedy probabilities known in reinforced learning. We show that the entropy minimization -- in contrast to its maximization -- leads to rudimentary forms of intelligent behavior: (i) the agent accounts for extreme events, especially when he did not invest much into adaptation. (ii) He chooses the action related to lesser loss (lesser of two evils) when confronted with two actions with comparable losses. (iii) The agent is subject to effects similar to cognitive dissonance and frustration. Neither of these features are shown by the risk-seeking agent whose probabilities are given by the maximum entropy. Mathematically, the difference between entropy maximization versus its minimization corresponds with maximizing a convex function (in a convex domain, i.e.convex programming) versus minimizing it (concave programming).

[94]  arXiv:1803.06648 (cross-list from physics.bio-ph) [pdf, other]
Title: Charge migration mechanisms in the DNA at finite temperature revisited; from quasi-ballistic to subdiffusive transport
Subjects: Biological Physics (physics.bio-ph); Mesoscale and Nanoscale Physics (cond-mat.mes-hall)

Various charge migration mechanisms in the DNA are studied within the framework of the Peyrard-Bishop-Holstein model which has been widely used to address charge dynamics in this macromolecule. To analyze these mechanisms we consider characteristic size and time scales of the fluctuations of the electronic and vibrational subsystems. It is shown, in particular, that due to substantial differences in these timescales polaron formation is unlikely within a broad range of temperatures. We demonstrate that at low temperatures electronic transport can be quasi-ballistic. For high temperatures, we propose an alternative to polaronic charge migration mechanism: the fluctuation-assisted one, in which the electron dynamics is governed by relatively slow fluctuations of the vibrational subsystem. We argue also that the discussed methods and mechanisms can be relevant for other organic macromolecular systems, such as conjugated polymers and molecular aggregates.

[95]  arXiv:1803.06658 (cross-list from physics.chem-ph) [pdf]
Title: Temperature dependent dynamics in water-ethanol liquid mixtures
Subjects: Chemical Physics (physics.chem-ph); Soft Condensed Matter (cond-mat.soft)

Temperature dependent hydrogen bond energetics and dynamical features, such as the diffusion coefficient and reorientational times, have been determined for ethanol-water mixtures with 10, 20 and 30 mol % of ethanol. Concerning pairwise interaction energies between molecules, it is found that water-water interactions become stronger, while ethanol-ethanol ones become significantly weaker in the mixtures than the corresponding values characteristic to the pure substances. Concerning the diffusion processes, for all concentrations the activation barrier of water and ethanol molecule become very similar to each other. Reorientation motions of water and ethanol become slower as ethanol concentration is increasing. Characteristic reorientational times of water in the mixtures are substantially longer than these values in the pure substance. On the other hand, this change for ethanol is only moderate. The reorientation motions of water (especially the ones related to the H-bonded interaction) become very similar for those of ethanol in the mixtures.

[96]  arXiv:1803.06722 (cross-list from quant-ph) [pdf, ps, other]
Title: Excluding joint probabilities from quantum theory
Comments: 5 pages, no figures, Rapid Communication
Journal-ref: Phys. Rev. A 97, 030102(R) (2018)
Subjects: Quantum Physics (quant-ph); Statistical Mechanics (cond-mat.stat-mech); Data Analysis, Statistics and Probability (physics.data-an)

Quantum theory does not provide a unique definition for the joint probability of two non-commuting observables, which is the next important question after the Born's probability for a single observable. Instead, various definitions were suggested, e.g. via quasi-probabilities or via hidden-variable theories. After reviewing open issues of the joint probability, we relate it to quantum imprecise probabilities, which are non-contextual and are consistent with all constraints expected from a quantum probability. We study two non-commuting observables in a two-dimensional Hilbert space and show that there is no precise joint probability that applies for any quantum state and is consistent with imprecise probabilities. This contrasts to theorems by Bell and Kochen-Specker that exclude joint probabilities for more than two non-commuting observables, in Hilbert space with dimension larger than two. If measurement contexts are included into the definition, joint probabilities are not anymore excluded, but they are still constrained by imprecise probabilities.

[97]  arXiv:1803.06724 (cross-list from quant-ph) [pdf, other]
Title: Melting a Hubbard dimer: benchmarks of `ALDA' for quantum thermodynamics
Subjects: Quantum Physics (quant-ph); Materials Science (cond-mat.mtrl-sci); Strongly Correlated Electrons (cond-mat.str-el)

The competition between evolution time, interaction strength, and temperature challenges our understanding of many-body quantum systems out-of-equilibrium. Here we consider a benchmark system, the Hubbard dimer, which allows us to explore all the relevant regimes and calculate exactly the related average quantum work. At difference with previous studies, we focus on the effect of increasing temperature, and show how this can turn competition between many-body interactions and driving field into synergy. We then turn to use recently proposed protocols inspired by density functional theory to explore if these effects could be reproduced by using simple approximations. We find that, up to and including intermediate temperatures, a method which borrows from ground-state adiabatic local density approximation improves dramatically the estimate for the average quantum work, including, in the adiabatic regime, when correlations are strong. However at high temperature and at least when based on the pseudo-LDA, this method fails to capture the counterintuitive qualitative dependence of the quantum work with interaction strength, albeit getting the quantitative estimates relatively close to the exact results.

[98]  arXiv:1803.06751 (cross-list from physics.bio-ph) [pdf]
Title: Plasmonic Toroidal Metamolecules Assembled by DNA Origami
Comments: 4 figures
Journal-ref: J. Am. Chem. Soc. 138, 5495 (2016)
Subjects: Biological Physics (physics.bio-ph); Soft Condensed Matter (cond-mat.soft)

We demonstrate hierarchical assembly of plasmonic toroidal metamolecules, which exhibit tailored optical activity in the visible spectral range. Each metamolecule consists of four identical origami-templated helical building blocks. Such toroidal metamolecules show stronger chiroptical response than monomers and dimers of the helical building blocks. Enantiomers of the plasmonic structures yield opposite circular dichroism spectra. The experimental results agree well with the theoretical simulations. We also demonstrate that given the circular symmetry of the structures, distinct chiroptical response along their axial orientation can be uncovered via simple spin-coating of the metamolecules on substrates. Our work provides a new strategy to create plasmonic chiral platforms with sophisticated nanoscale architectures for potential applications such as chiral sensing using chemically-based assembly systems.

[99]  arXiv:1803.06753 (cross-list from physics.bio-ph) [pdf]
Title: DNA nanotechnology-enabled chiral plasmonics: from static to dynamic
Comments: 7 figures
Journal-ref: Acc. Chem. Res. 50, 2906 (2017)
Subjects: Biological Physics (physics.bio-ph); Soft Condensed Matter (cond-mat.soft)

In this Account, we discuss a variety of static and dynamic chiral plasmonic nanostructures enabled by DNA nanotechnology. In the category of static plasmonic systems, we first show chiral plasmonic nanostructures based on spherical AuNPs, including plasmonic helices, toroids, and tetramers. To enhance the CD responses, anisotropic gold nanorods with larger extinction coefficients are utilized to create chiral plasmonic crosses and helical superstructures. Next, we highlight the inevitable evolution from static to dynamic plasmonic systems along with the fast development of this interdisciplinary field. Several dynamic plasmonic systems are reviewed according to their working mechanisms.

[100]  arXiv:1803.06767 (cross-list from quant-ph) [pdf, other]
Title: Generation and detection of non-Gaussian phonon-added coherent states in optomechanical systems
Comments: 5+4 pages, 3+1 figures
Subjects: Quantum Physics (quant-ph); Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Optics (physics.optics)

Adding excitations on a coherent state provides an effective way to observe nonclassical properties of radiation fields. Here we describe and analyse how to apply this concept to the motional state of a mechanical oscillator and present a full scheme to prepare non-Gaussian {\it phonon}-added coherent states of the mechanical motion in cavity optomechanics. We first generate a mechanical coherent state using electromagnetically induced transparency. We then add a single phonon onto the coherent state via optomechanical parametric down-conversion combined with single photon detection. We validate this single-phonon-added coherent state by using a red-detuned beam and reading out the state of the optical output field. This approach allows us to verify nonclassical properties of the phonon state, such as sub-Poissonian character and quadrature squeezing. We further show that our scheme can be directly implemented using existing devices, and is generic in nature and hence applicable to a variety of systems in opto- and electromechanics.

[101]  arXiv:1803.06808 (cross-list from math-ph) [pdf, other]
Title: Local martingales associated with SLE with internal symmetry
Authors: Shinji Koshida
Comments: 45 pages
Subjects: Mathematical Physics (math-ph); Statistical Mechanics (cond-mat.stat-mech); Probability (math.PR); Quantum Algebra (math.QA); Representation Theory (math.RT)

We consider Schramm-Loewner evolutions with internal degrees of freedom that are associated with representations of affine Lie algebras, following the group theoretical formulation of SLE. We observe that SLEs considered by Bettelheim et al. [PRL 95, 251601 (2005)] and Alekseev et al. [Lett. Math. Phys. 97, 243-261 (2011)] in correlation function formulation are reconstrunced. We also explicitly write down stochastic differential equations on internal degrees of freedom for Heisenberg algebras and the affine $\mathfrak{sl}_{2}$. Our formulation enables to write down several local martingales associated with the solution of SLE from computation on a representation of an affine Lie algebra. Indeed, we write down local martingales associated with solution of SLE for Heisenberg algebras and the affine $\mathfrak{sl}_{2}$. We also find affine $\mathfrak{sl}_{2}$ symmetry of a space of SLE local martingales for the affine $\mathfrak{sl}_{2}$, which can be extended to other affine Lie algebras.

[102]  arXiv:1803.06812 (cross-list from quant-ph) [pdf, other]
Title: Quantifying the effect of interactions in quantum many-body systems
Comments: 24 pages, 8 figures; submission to SciPost
Subjects: Quantum Physics (quant-ph); Statistical Mechanics (cond-mat.stat-mech); Strongly Correlated Electrons (cond-mat.str-el)

Free fermion systems enjoy a privileged place in physics. With their simple structure they can explain a variety of effects, ranging from insulating and metallic behaviours to superconductivity and the integer quantum Hall effect. Interactions, e.g. in the form of Coulomb repulsion, can dramatically alter this picture by giving rise to emerging physics that may not resemble free fermions. Examples of such phenomena include high-temperature superconductivity, fractional quantum Hall effect, Kondo effect and quantum spin liquids. The non-perturbative behaviour of such systems remains a major obstacle to their theoretical understanding that could unlock further technological applications. Here, we present a pedagogical review of "interaction distance" [Nat. Commun. 8, 14926 (2017)] -- a systematic method that quantifies the effect interactions can have on the energy spectrum and on the quantum correlations of generic many-body systems. In particular, the interaction distance is a diagnostic tool that identifies the emergent physics of interacting systems. We illustrate this method on the simple example of a one-dimensional Fermi-Hubbard dimer.

[103]  arXiv:1803.06861 (cross-list from physics.soc-ph) [pdf, ps, other]
Title: Analytical and numerical study of the non-linear noisy voter model on complex networks
Subjects: Physics and Society (physics.soc-ph); Statistical Mechanics (cond-mat.stat-mech)

We study the noisy voter model using a specific non-linear dependence of the rates that takes into account collective interaction between individuals. The resulting model is solved exactly under the all-to-all coupling configuration and approximately in some random networks environments. In the all-to-all setup we find that the non-linear interactions induce "bona fide" phase transitions that, contrarily to the linear version of the model, survive in the thermodynamic limit. The main effect of the complex network is to shift the transition lines and modify the finite-size dependence, a modification that can be captured with the introduction of an effective system size that decreases with the degree heterogeneity of the network. A non-trivial finite-size dependence of the moments of the probability distribution is derived from our treatment, nevertheless mean-field exponents are obtained in the thermodynamic limit. These theoretical predictions are well confirmed by numerical simulations of the stochastic process.

[104]  arXiv:1803.06938 (cross-list from hep-th) [pdf, other]
Title: Conformal amplitude hierarchy and the Poincare disk
Authors: Hirohiko Shimada
Comments: 13 pages, 2 figures. see this version; corrections made; references added
Journal-ref: J. Phys.: Conf. Ser. 965 (2018) 012036
Subjects: High Energy Physics - Theory (hep-th); Statistical Mechanics (cond-mat.stat-mech); Mathematical Physics (math-ph)

The amplitude for the singlet channels in the 4-point function of the fundamental field in the conformal field theory of the 2d $O(n)$ model is studied as a function of $n$. For a generic value of $n$, the 4-point function has infinitely many amplitudes, whose landscape can be very spiky as the higher amplitude changes its sign many times at the simple poles, which generalize the unique pole of the energy operator amplitude at $n=0$. In the stadard parameterization of $n$ by angle in unit of $\pi$, we find that the zeros and poles happen at the rational angles, forming a hierarchical tree structure inherent in the Poincar\'{e} disk. Some relation between the amplitude and the Farey path, a piecewise geodesic that visits these zeros and poles, is suggested. In this hierarchy, the symmetry of the congruence subgroup $\Gamma(2)$ of $SL(2,\mathbb{Z})$ naturally arises from the two clearly distinct even/odd classes of the rational angles, in which one respectively gets the truncated operator algebras and the logarithmic 4-point functions.

[105]  arXiv:1803.06950 (cross-list from physics.ins-det) [pdf, other]
Title: Study of point- and cluster-defects in radiation-damaged silicon
Comments: 13 pages, 12 figures, 4 tables
Subjects: Instrumentation and Detectors (physics.ins-det); Materials Science (cond-mat.mtrl-sci)

Non-ionising energy loss of radiation produces point defects and defect clusters in silicon, which result in a signifcant degradation of sensor performance. In this contribution results from TSC (Thermally Stimulated Current) defect spectroscopy for silicon pad diodes irradiated by electrons to fluences of a few $10^{14}$ cm$^{-2}$ and energies between 3.5 and 27 MeV for isochronal annealing between 80 and 280{\deg}C, are presented. A method based on SRH (Shockley-Read-Hall) statistics is introduced, which assumes that the ionisation energy of the defects in a cluster depends on the fraction of occupied traps. The dfference of ionisation energy of an isolated point defect and a fully occupied cluster, $\Delta E_a$, is extracted from the TSC data.
For the VOi (vacancy-oxygen interstitial) defect $\Delta E_a = 0$ is found, which cofirms that it is a point defect, and validates the method for point defects. For clusters made of deep acceptors the $\Delta E_a$ values for different defects are determined after annealing at 80{\deg}C as a function of electron energy, and for the irradiation with 15 MeV electrons as a function of annealing temperature. For the irradiation with 3.5 MeV electrons the value $\Delta E_a = 0$ is found, whereas for the electron energies of 6 to 27 MeV $\Delta E_a > 0$. This agrees with the expected threshold of about 5 MeV for cluster formation by electrons. The $\Delta E_a$ values determined as a function of annealing temperature show that the annealing rate is different for different defects. A naive diffusion model is used to estimate the temperature dependencies of the diffusion of the defects in the clusters.

[106]  arXiv:1803.06969 (cross-list from stat.ML) [pdf, ps, other]
Title: Comparing Dynamics: Deep Neural Networks versus Glassy Systems
Comments: 5 figures
Subjects: Machine Learning (stat.ML); Disordered Systems and Neural Networks (cond-mat.dis-nn); Learning (cs.LG)

We analyze numerically the training dynamics of deep neural networks (DNN) by using methods developed in statistical physics of glassy systems. The two main issues we address are the complexity of the loss-landscape and of the dynamics within it, and to what extent DNNs share similarities with glassy systems. Our findings, obtained for different architectures and datasets, suggest that during the training process the dynamics slows down because of an increasingly large number of flat directions. At large times, when the loss is approaching zero, the system diffuses at the bottom of the landscape. Despite some similarities with the dynamics of mean-field glassy systems, in particular, the absence of barrier crossing, we find distinctive dynamical behaviors in the two cases, showing that the statistical properties of the corresponding loss and energy landscapes are different. In contrast, when the network is under-parametrized we observe a typical glassy behavior, thus suggesting the existence of different phases depending on whether the network is under-parametrized or over-parametrized.

[107]  arXiv:1803.07014 (cross-list from quant-ph) [pdf, other]
Title: Two-photon interference in the telecom C-band after frequency conversion of photons from remote quantum emitters
Authors: Jonas H. Weber (1), Benjamin Kambs (2), Jan Kettler (1), Simon Kern (1), Julian Maisch (1), Hüseyin Vural (1), Michael Jetter (1), Simone L. Portalupi (1), Christoph Becher (2), Peter Michler (1) ((1) Institut für Halbleiteroptik und Funktionelle Grenzflächen, Center for Integrated Quantum Science and Technology (IQST) and SCoPE, University of Stuttgart, Allmandring 3, 70569 Stuttgart, Germany, (2) Fachrichtung Physik, Universität des Saarlandes, Campus E 2.6, 66123 Saarbrücken, Germany)
Comments: J. H. Weber and B. Kambs contributed equally to this work
Subjects: Quantum Physics (quant-ph); Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Applied Physics (physics.app-ph); Optics (physics.optics)

Efficient fiber-based long-distance quantum communication via quantum repeaters relies on deterministic single-photon sources at telecom wavelengths, with the potential to exploit the existing world-wide infrastructures. For upscaling the experimental complexity in quantum networking, two-photon interference (TPI) of remote non-classical emitters in the low-loss telecom bands is of utmost importance. With respect to TPI of distinct emitters, several experiments have been conducted, e.g., using trapped atoms [Beugnon2006], ions [Maunz2007], NV-centers [Bernien2012, Sipahigil2012], SiV-centers [Sipahigil2014], organic molecules [Lettow2010] and semiconductor quantum dots (QDs) [Patel2010, Flagg2010, He2013b, Gold2014, Giesz2015, Thoma2017, Reindl2017, Zopf2017]; however, the spectral range was far from the highly desirable telecom C-band. Here, we report on TPI at 1550 nm between down-converted single photons from remote QDs [Michler2017Book], demonstrating quantum frequency conversion [Zaske2012, Ates2012, Kambs2016] as precise and stable mechanism to erase the frequency difference between independent emitters. On resonance, a TPI-visibility of (29+-3)% has been observed, being only limited by spectral diffusion processes of the individual QDs [Robinson2000, Kuhlmann2015]. Up to 2-km of additional fiber channel has been introduced in both or individual signal paths with no influence on TPI-visibility, proving negligible photon wave-packet distortion. The present experiment is conducted within a local fiber network covering several rooms between two floors of the building. Our studies pave the way to establish long-distance entanglement distribution between remote solid-state emitters including interfaces with various quantum hybrid systems [DeGreve2012,Maring2017,Bock2017,Maring2018].

[108]  arXiv:1803.07070 (cross-list from hep-th) [pdf, ps, other]
Title: An entropy current in superspace
Comments: 20 pages
Subjects: High Energy Physics - Theory (hep-th); Statistical Mechanics (cond-mat.stat-mech)

We construct an entropy current using a supersymmetric formulation of the low-energy effective action for the Schwinger-Keldysh generating functional. We define an entropy current quantum mechanically by coupling it to an external source. It is given by the bottom component of an entropy current superfield which is conserved in superspace, but when restricted to real space satisfies a non-conservation law. Our analysis is valid in the probe limit which allows us to fully treat quantum fluctuations.

Replacements for Tue, 20 Mar 18

[109]  arXiv:1605.00396 (replaced) [pdf, other]
Title: Low temperature thermodynamic investigation of the phase diagram of Sr$_3$Ru$_2$O$_7$
Journal-ref: Phys. Rev. B 97, 115101 (2018)
Subjects: Strongly Correlated Electrons (cond-mat.str-el)
[110]  arXiv:1607.04478 (replaced) [pdf, ps, other]
Title: Viscosity and effective temperature of an active dense system of self-propelled particles
Comments: Total 7 pages
Subjects: Soft Condensed Matter (cond-mat.soft); Statistical Mechanics (cond-mat.stat-mech); Biological Physics (physics.bio-ph)
[111]  arXiv:1610.00223 (replaced) [pdf, other]
Title: Universal relations and normal phase of an ultracold Fermi gas with coexisting $s$- and $p$-wave interactions
Comments: 10 pages, 5 figures, updated references, published version
Journal-ref: Phys. Rev. A 94, 063616 (2016)
Subjects: Quantum Gases (cond-mat.quant-gas)
[112]  arXiv:1612.06692 (replaced) [pdf, ps, other]
Title: Adaptive cluster approximation for reduced density-matrix functional theory
Comments: 12 pages, 4 figures
Subjects: Strongly Correlated Electrons (cond-mat.str-el)
[113]  arXiv:1701.04903 (replaced) [pdf, other]
Title: The Landau-Lifshitz equation, the NLS, and the magnetic rogue wave as a by-product of two colliding regular "positons"
Comments: 25 pages, 9 figures. Added Section 7 ("7. One last remark: But what of generalization?.."), corrected a number of typos, added 2 more references
Subjects: Exactly Solvable and Integrable Systems (nlin.SI); Materials Science (cond-mat.mtrl-sci)
[114]  arXiv:1703.04401 (replaced) [pdf, other]
Title: Soft inclusion in a confined fluctuating active gel
Comments: 16 pages, 9 figures
Journal-ref: Physical Review E, 97, 032602 (2018)
Subjects: Biological Physics (physics.bio-ph); Soft Condensed Matter (cond-mat.soft); Statistical Mechanics (cond-mat.stat-mech)
[115]  arXiv:1703.05371 (replaced) [pdf, other]
Title: Directional Sensitivity In Light-Mass Dark Matter Searches With Single-Electron Resolution Ionization Detectors
Comments: Most recent version
Subjects: Instrumentation and Detectors (physics.ins-det); Cosmology and Nongalactic Astrophysics (astro-ph.CO); Materials Science (cond-mat.mtrl-sci); High Energy Physics - Experiment (hep-ex); Computational Physics (physics.comp-ph)
[116]  arXiv:1703.09481 (replaced) [pdf, ps, other]
Title: Metastable Markov chains: from the convergence of the trace to the convergence of the finite-dimensional distributions
Subjects: Probability (math.PR); Statistical Mechanics (cond-mat.stat-mech)
[117]  arXiv:1706.01822 (replaced) [pdf, other]
Title: Calculation of the critical temperature of a dilute Bose gas in the Bogoliubov approximation
Comments: Published version, 7 pages, 2 figures
Subjects: Quantum Gases (cond-mat.quant-gas); Mathematical Physics (math-ph)
[118]  arXiv:1706.04406 (replaced) [pdf, other]
Title: Fermion bound states in geometrically deformed backgrounds
Comments: 8 pages, 12 figures; text and new references added
Subjects: High Energy Physics - Theory (hep-th); Mesoscale and Nanoscale Physics (cond-mat.mes-hall); High Energy Physics - Phenomenology (hep-ph)
[119]  arXiv:1706.04864 (replaced) [pdf, other]
Title: Generation of atypical hopping and interactions by kinetic driving
Comments: Paper revised and expanded. Sections IV-B, IV-C, V and VI have been added. Figs. 6-9 are new
Subjects: Quantum Gases (cond-mat.quant-gas)
[120]  arXiv:1706.06074 (replaced) [pdf]
Title: Evidence for Majorana bound state in an iron-based superconductor
Comments: 27 pages, 11 figures, supplementary information included
Subjects: Superconductivity (cond-mat.supr-con)
[121]  arXiv:1706.06747 (replaced) [pdf, ps, other]
Title: Bounds on quantum confinement effects in metal nanoparticles
Comments: 11 pages, 6 figures
Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Optics (physics.optics)
[122]  arXiv:1706.09779 (replaced) [pdf, other]
Title: Deep neural networks for direct, featureless learning through observation: the case of 2d spin models
Journal-ref: Phys. Rev. E 97, 032119 - Published 16 March 2018
Subjects: Materials Science (cond-mat.mtrl-sci)
[123]  arXiv:1706.09923 (replaced) [pdf, ps, other]
Title: A study of the dense Uniform Electron Gas with high orders of Coupled Cluster
Comments: This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. The following article appeared in "Neufeld, V.A. and Thom, A.J.W., J. Chem. Phys. 147, 194105 (2017)" and may be found at this https URL (following this https URL)
Journal-ref: J. Chem. Phys. 147, 194105 (2017)
Subjects: Chemical Physics (physics.chem-ph); Strongly Correlated Electrons (cond-mat.str-el)
[124]  arXiv:1707.04963 (replaced) [pdf, other]
Title: A large class of solvable multistate Landau-Zener models and quantum integrability
Comments: The 2nd version contains considerable changes, including new sections, that are based on recent advances in arXiv/1711.09945 (new Ref.[1])
Subjects: Quantum Physics (quant-ph); Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Mathematical Physics (math-ph)
[125]  arXiv:1707.06419 (replaced) [pdf, other]
Title: Quantum Degenerate Majorana Surface Modes in Two-Dimensional Continuous Space
Comments: 6+7 pages, 3+1 figures, with supplemental material
Subjects: Quantum Gases (cond-mat.quant-gas); Superconductivity (cond-mat.supr-con)
[126]  arXiv:1707.06447 (replaced) [pdf, other]
Title: On spinodal points and Lee-Yang edge singularities
Comments: 26 pages, 8 figures; v2: shortened Sec. 4.1 and streamlined arguments/notation in Sec. 4.2, details moved to appendix, added reference 17
Journal-ref: J. Stat. Mech. (2018) 033207
Subjects: High Energy Physics - Theory (hep-th); Statistical Mechanics (cond-mat.stat-mech); Nuclear Theory (nucl-th)
[127]  arXiv:1708.00165 (replaced) [pdf, other]
Title: Ordering dynamics of self-propelled particles in an inhomogeneous medium
Subjects: Statistical Mechanics (cond-mat.stat-mech); Soft Condensed Matter (cond-mat.soft); Biological Physics (physics.bio-ph)
[128]  arXiv:1708.06661 (replaced) [pdf, ps, other]
Title: Highly Confined Stacks of Graphene Oxide Sheets in Water
Comments: 11 pages, 10 figures
Journal-ref: European Physical Journal E (2018) 41:30
Subjects: Soft Condensed Matter (cond-mat.soft)
[129]  arXiv:1709.03704 (replaced) [pdf, other]
Title: Full-Counting Many-Particle Dynamics: Nonlocal and Chiral Propagation of Correlations
Comments: 6+8 pages, 3+3 figures
Subjects: Quantum Gases (cond-mat.quant-gas); Statistical Mechanics (cond-mat.stat-mech); Quantum Physics (quant-ph)
[130]  arXiv:1709.04160 (replaced) [pdf, ps, other]
Title: Scaling Law for Three-body Collisions in Identical Fermions with $p$-wave Interactions
Comments: 5 pages, 4 figures
Subjects: Quantum Gases (cond-mat.quant-gas); Atomic Physics (physics.atom-ph)
[131]  arXiv:1709.05198 (replaced) [pdf]
Title: Tunable viscosity modification with diluted particles: When particles decrease the viscosity of complex fluids
Comments: 13+7 pages, 6+7 figures
Subjects: Soft Condensed Matter (cond-mat.soft); Fluid Dynamics (physics.flu-dyn)
[132]  arXiv:1710.01954 (replaced) [pdf, ps, other]
Title: Actuated rheology of magnetic micro-swimmers suspensions : emergence of motor and brake states
Comments: 10 pages, 6 figures, accepted in PRFluids
Subjects: Biological Physics (physics.bio-ph); Soft Condensed Matter (cond-mat.soft); Fluid Dynamics (physics.flu-dyn)
[133]  arXiv:1710.03258 (replaced) [pdf, ps, other]
Title: Phases Of Adjoint QCD$_3$ And Dualities
Comments: 41 pages, 19 figures; new tests of the proposal and additional references. references added. small additions and typos corrected
Subjects: High Energy Physics - Theory (hep-th); Strongly Correlated Electrons (cond-mat.str-el)
[134]  arXiv:1710.04159 (replaced) [pdf, other]
Title: Stabilization and control of Majorana bound states with elongated skyrmions
Journal-ref: Phys. Rev. B 97 115136 (2018)
Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Superconductivity (cond-mat.supr-con)
[135]  arXiv:1710.06983 (replaced) [pdf, other]
Title: Design of high-strength refractory complex solid-solution alloys
Comments: 9 pages, 6 figures
Subjects: Materials Science (cond-mat.mtrl-sci)
[136]  arXiv:1710.09174 (replaced) [pdf, other]
Title: Casimir self-stress in a dielectric sphere
Subjects: Quantum Physics (quant-ph); Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
[137]  arXiv:1711.01713 (replaced) [pdf]
Title: Determination of layer-dependent exciton binding energies in few-layer black phosphorus
Comments: updated version, now 2 layer BP exciton binding energy is included
Journal-ref: Science Advances,Vol. 4, no. 3, eaap9977 (2018)
Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
[138]  arXiv:1711.02146 (replaced) [pdf, other]
Title: Analysis and Optimization of Population Annealing
Comments: 13 pages, 6 figures; journal version
Journal-ref: Phys. Rev. E 97, 033301 (2018)
Subjects: Statistical Mechanics (cond-mat.stat-mech)
[139]  arXiv:1711.02728 (replaced) [pdf, other]
Title: Jamming and condensation in one-dimensional driven flow
Comments: 12 pages, 10 figures (10 pdf files); published version
Journal-ref: Phys. Rev. E 97, 032120 (2018)
Subjects: Statistical Mechanics (cond-mat.stat-mech); Disordered Systems and Neural Networks (cond-mat.dis-nn)
[140]  arXiv:1711.02991 (replaced) [pdf, ps, other]
Title: Effect of density of states peculiarities on Hund's metal behavior
Comments: 7 pages, 7 figures
Subjects: Strongly Correlated Electrons (cond-mat.str-el)
[141]  arXiv:1711.05317 (replaced) [pdf, ps, other]
Title: Correlated network of networks enhances robustness against catastrophic failures
Comments: 5 figures
Subjects: Physics and Society (physics.soc-ph); Statistical Mechanics (cond-mat.stat-mech)
[142]  arXiv:1711.06602 (replaced) [pdf, other]
Title: Klein tunneling and electron optics in Dirac-Weyl fermion systems with tilted energy dispersion
Comments: 5 pages, 5 figures and Supplemental Material, submitted for publication
Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
[143]  arXiv:1711.10930 (replaced) [pdf, ps, other]
Title: Two types of criticality in the brain
Subjects: Disordered Systems and Neural Networks (cond-mat.dis-nn); Neurons and Cognition (q-bio.NC)
[144]  arXiv:1712.00039 (replaced) [pdf, other]
Title: Effective interactions in a quantum Bose-Bose mixture
Comments: 14 pages, 5 figures
Subjects: Quantum Gases (cond-mat.quant-gas)
[145]  arXiv:1712.01884 (replaced) [pdf, other]
Title: 3D non-Fermi liquid behavior from 1D quantum critical local moments
Comments: 5+8 pages, 2+1 figures
Subjects: Strongly Correlated Electrons (cond-mat.str-el)
[146]  arXiv:1712.02144 (replaced) [pdf, ps, other]
Title: Dual Origin of Room Temperature Sub-Terahertz Photoresponse in Graphene Field Effect Transistors
Comments: 5 pages + 5 pages Supplementary information
Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
[147]  arXiv:1712.06280 (replaced) [pdf, other]
Title: Dipole-like dynamical nuclear spin polarization around a quantum point contact
Comments: 17 pages, 8 figures; referees' comments incorporated, some typos corrected, footnotes' format changed
Journal-ref: Phys. Rev. B 97, 075440 (2018)
Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
[148]  arXiv:1712.06561 (replaced) [pdf, ps, other]
Title: Soft pair excitations and double-log divergences due to carrier interactions in graphene
Comments: 6pgs, 1fg
Journal-ref: Phys. Rev. B 97, (115423) 2018
Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
[149]  arXiv:1801.02295 (replaced) [pdf, other]
Title: Interatomic interaction effects on second-order momentum correlations and Hong-Ou-Mandel interference of double-well-trapped ultracold fermionic atoms
Comments: 18 pages, 8 color figures. A new section V was added; it describes entanglement aspects and the connection to the Hong-Ou-Mandel interference physics. Also the whole range for both repulsive and attractive interparticle interaction is now investigated. For related papers, see this http URL
Subjects: Quantum Gases (cond-mat.quant-gas); Nuclear Theory (nucl-th); Quantum Physics (quant-ph)
[150]  arXiv:1801.03021 (replaced) [pdf, other]
Title: Stratification of mixtures in evaporating liquid films occurs only for a range of volume fractions of the smaller component
Authors: Richard P Sear
Comments: 8 pages, 5 figures
Subjects: Soft Condensed Matter (cond-mat.soft)
[151]  arXiv:1801.03726 (replaced) [pdf, other]
Title: Large deviation theory for diluted Wishart random matrices
Comments: 10 pages, 6 figures
Journal-ref: Phys. Rev. E 97, 032124 (2018)
Subjects: Disordered Systems and Neural Networks (cond-mat.dis-nn); Statistical Mechanics (cond-mat.stat-mech); Data Analysis, Statistics and Probability (physics.data-an)
[152]  arXiv:1801.05675 (replaced) [pdf, other]
Title: Tan's contact in a cigar-shaped dilute Bose gas
Subjects: Quantum Gases (cond-mat.quant-gas)
[153]  arXiv:1801.06140 (replaced) [pdf, other]
Title: Enhanced polymer capture speed and extended translocation time in pressure-solvation traps
Authors: Sahin Buyukdagli
Subjects: Soft Condensed Matter (cond-mat.soft)
[154]  arXiv:1801.06890 (replaced) [pdf, other]
Title: Isomorph theory of physical aging
Authors: Jeppe C. Dyre
Subjects: Soft Condensed Matter (cond-mat.soft); Statistical Mechanics (cond-mat.stat-mech)
[155]  arXiv:1801.07448 (replaced) [pdf, other]
Title: High-momentum tail and universal relations of a Fermi gas near a Raman-dressed Feshbach resonance
Comments: 10 pages, 6 figures, update references, published version
Journal-ref: Phys. Rev. A 97, 033610 (2018)
Subjects: Quantum Gases (cond-mat.quant-gas)
[156]  arXiv:1801.07659 (replaced) [pdf, other]
Title: Multicritical points of the O(N) scalar theory in $2<d<4$ for large N
Authors: A. Katsis, N. Tetradis (Athens U.)
Comments: 10 pages, 3 figures, minor corrections
Subjects: Statistical Mechanics (cond-mat.stat-mech); High Energy Physics - Theory (hep-th)
[157]  arXiv:1801.09388 (replaced) [pdf, ps, other]
Title: Quantum metric contribution to the pair mass in spin-orbit coupled Fermi superfluids
Authors: M. Iskin
Comments: 6 pages with 2 figures; to appear in PRA
Subjects: Quantum Gases (cond-mat.quant-gas); Strongly Correlated Electrons (cond-mat.str-el); Superconductivity (cond-mat.supr-con)
[158]  arXiv:1801.09492 (replaced) [pdf, ps, other]
Title: Heterogeneity effects in power-grid network models
Comments: 12 pages, 10 Figures, results recalculated following K/N -&gt; K/N_i coupling renormalization
Subjects: Physics and Society (physics.soc-ph); Disordered Systems and Neural Networks (cond-mat.dis-nn); Statistical Mechanics (cond-mat.stat-mech)
[159]  arXiv:1801.09655 (replaced) [pdf, other]
Title: Real space mapping of topological invariants using artificial neural networks
Comments: 9 pages, 6 figures
Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
[160]  arXiv:1801.10150 (replaced) [pdf, other]
Title: Odd surface waves in two-dimensional incompressible fluids
Comments: 34 pages, 7 figures, revised version: added discussion on the Hamiltonian structure and conservation laws, new references added, minor typos corrected
Subjects: Fluid Dynamics (physics.flu-dyn); Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
[161]  arXiv:1802.02010 (replaced) [pdf, ps, other]
Title: Effects of interaction imbalance in a strongly repulsive one-dimensional Bose gas
Comments: 8 pages, 2 figures
Journal-ref: Few-Body Syst (2018) 59: 22
Subjects: Quantum Gases (cond-mat.quant-gas); Quantum Physics (quant-ph)
[162]  arXiv:1802.02768 (replaced) [pdf, other]
Title: Hyperelastic constitutive modeling with exponential decay and application to a viscoelastic adhesive
Subjects: Materials Science (cond-mat.mtrl-sci)
[163]  arXiv:1802.04210 (replaced) [pdf, other]
Title: Selective Area Grown Semiconductor-Superconductor Hybrids: A Basis for Topological Networks
Comments: NBI QDEV 2018
Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Materials Science (cond-mat.mtrl-sci); Superconductivity (cond-mat.supr-con)
[164]  arXiv:1802.06744 (replaced) [pdf, other]
Title: Thermal stability of metastable magnetic skyrmions: Entropic narrowing and significance of internal eigenmodes
Comments: 12 pages, 8 figures
Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Statistical Mechanics (cond-mat.stat-mech)
[165]  arXiv:1802.06979 (replaced) [pdf]
Title: Electrical Control of 2D Magnetism in Bilayer CrI3
Comments: To appear in Nature Nanotechnology
Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
[166]  arXiv:1802.08696 (replaced) [pdf, other]
Title: Correlation functions of the quantum sine-Gordon model in and out of equilibrium
Comments: Animation of quench dynamics in ancillary material: this https URL Version 2: improved presentation
Subjects: Statistical Mechanics (cond-mat.stat-mech); Quantum Gases (cond-mat.quant-gas); High Energy Physics - Theory (hep-th); Quantum Physics (quant-ph)
[167]  arXiv:1802.10584 (replaced) [pdf, other]
[168]  arXiv:1803.00371 (replaced) [pdf, other]
Title: Possible three-dimensional nematic odd-parity superconductivity in Sr$_2$RuO$_4$
Authors: Wen Huang, Hong Yao
Comments: 4 plus pages + supplemental materials. Minor edits
Subjects: Superconductivity (cond-mat.supr-con)
[169]  arXiv:1803.00975 (replaced) [pdf, ps, other]
Title: Entangled Pauli Principles: the DNA of Quantum Hall Fluids
Authors: Sumanta Bandyopadhyay (1), Li Chen (2), Mostafa Tanhayi Ahari (3), Gerardo Ortiz (1 and 3), Zohar Nussinov (1), Alexander Seidel (1) ((1) Department of Physics, Washington University, (2) National High Magnetic Field Laboratory and Department of Physics, Florida State University, (3) Department of Physics, Indiana University)
Comments: 12 pages, including supplemental. Revised version includes two references corresponding to multi-layer graphene
Subjects: Strongly Correlated Electrons (cond-mat.str-el)
[170]  arXiv:1803.01894 (replaced) [pdf, ps, other]
Title: Radiative recombination of large polarons in halide perovskites
Comments: 9 pages, 6 figures
Subjects: Materials Science (cond-mat.mtrl-sci)
[171]  arXiv:1803.02561 (replaced) [pdf, other]
Title: Theory on the optical spinpolarization loop of the nitrogen-vacancy center in diamond
Comments: 13 pages, 6 figures, 1 table
Subjects: Quantum Physics (quant-ph); Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
[172]  arXiv:1803.02618 (replaced) [pdf, other]
Title: Time-reversal symmetry breaking in superconductors through loop Josephson-current order
Comments: 6 pages, 3 figures (More references added)
Subjects: Superconductivity (cond-mat.supr-con)
[173]  arXiv:1803.03490 (replaced) [pdf, ps, other]
Title: Computing Transition Rates for Rare Event: When Kramers Theory meets Free Energy Landscape
Authors: François Sicard
Comments: 5 pages, 1 figure, Supplemental Material (6 pages, 3 figures)
Subjects: Statistical Mechanics (cond-mat.stat-mech); Soft Condensed Matter (cond-mat.soft); Biological Physics (physics.bio-ph); Computational Physics (physics.comp-ph)
[174]  arXiv:1803.03504 (replaced) [pdf]
Title: Synthesis And Characterization Of Polyynes End-Capped By Biphenyl Groups ({\Alpha},Ω-Biphenylpolyynes)
Comments: The research leading to these results has received funding from the European Research Council Consolidator Grant EspLORE (ERC-2016-CoG Grant No.724610)
Journal-ref: Carbon volume:126 pages:232-240 (2018)
Subjects: Materials Science (cond-mat.mtrl-sci)
[175]  arXiv:1803.04766 (replaced) [pdf, ps, other]
Title: Hydrogen Concentration in Photovoltaic a-Si:H Annealed at Different Temperatures Measured by Neutron Reflectometry
Comments: 4 pages, 5 figures
Subjects: Materials Science (cond-mat.mtrl-sci)
[176]  arXiv:1803.04788 (replaced) [pdf, ps, other]
Title: Efficient two-mode interferometers with spinor Bose-Einstein condensates
Comments: 13 pages, 6 figures
Subjects: Quantum Gases (cond-mat.quant-gas)
[177]  arXiv:1803.05561 (replaced) [pdf, other]
Title: On the exact continuous mapping of fermions
Comments: 7-page manuscript (2 figures) with 11-page supplemental material
Subjects: Chemical Physics (physics.chem-ph); Statistical Mechanics (cond-mat.stat-mech); Quantum Physics (quant-ph)
[178]  arXiv:1803.05841 (replaced) [pdf, ps, other]
Title: Impurity effect as a probe for the pairing symmetry of graphene-based superconductors
Comments: 5 pages, 6 figures
Subjects: Superconductivity (cond-mat.supr-con)
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