Found 28 papers in cond-mat
Date of feed: Thu, 01 Jun 2023 00:30:00 GMT

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Topologically-constrained fluctuations and thermodynamics regulate nonequilibrium response. (arXiv:2305.19348v1 [cond-mat.stat-mech])
Gabriela Fernandes Martins, Jordan M. Horowitz

Limits on a system's response to external perturbations inform our understanding of how physical properties can be shaped by microscopic characteristics. Here, we derive constraints on the steady-state nonequilibrium response of physical observables in terms of the topology of the microscopic state space and the strength of thermodynamic driving. Notably, evaluation of these limits requires no kinetic information beyond the state-space structure. When applied to models of receptor binding, we find that sensitivity is bounded by the steepness of a Hill function with a Hill coefficient enhanced by the chemical driving beyond the structural equilibrium limit.

A unified quasiparticle approach to the theory of strongly correlated electron liquids. (arXiv:2305.19385v1 [cond-mat.str-el])
V. A. Khodel, J. W. Clark, M. V. Zverev

Landau's quasiparticle formalism is generalized to describe a wide class of strongly correlated Fermi systems, in addition to conventional Fermi liquids. This class includes (i) so-called marginal exemplars and (ii) systems that harbor interaction-driven flat bands, in both of which manifestations of non-Fermi-liquid behavior are well documented. Specifically, the advent of such flat bands is attributed to a spontaneous topological rearrangement of the Landau state that supplements the conventional Landau quasiparticle picture with a different set of quasiparticles, the so-called fermion condensate, whose single-particle spectrum is dispersionless. The celebrated Landau-Luttinger theorem can then be extended to marginal Fermi liquids, in which the density of the augmented quasiparticle system is shown to coincide with the particle density. Moreover, the total density of systems hosting interaction-driven flat bands is shown to be the sum of the densities of the two quasiparticle subsystems: the Landau-like component and the fermion condensate. It is demonstrated that the formalism thus introduced serves to clarify the non-BCS nature of exotic superconductivity.

Bloch Oscillations, Landau-Zener Transition, and Topological Phase Evolution in a Pendula Array. (arXiv:2305.19387v1 [cond-mat.mes-hall])
Izhar Neder, Chaviva Sirote, Meital Geva, Yoav Lahini, Roni Ilan, Yair Shokef

We experimentally and theoretically study the dynamics of a one-dimensional array of pendula with a mild spatial gradient in their self-frequency and where neighboring pendula are connected with weak and alternating coupling. We map their dynamics to the topological Su-Schrieffer-Heeger (SSH) model of charged quantum particles on a lattice with alternating hopping rates in an external electric field. By directly tracking the dynamics of a wavepacket in the bulk of the lattice, we observe Bloch oscillations, Landau-Zener transitions, and coupling between the isospin (i.e. the inner wave function distribution within the unit cell) and the spatial degrees of freedom (the distribution between unit cells). We then use Bloch oscillations in the bulk to directly measure the non-trivial global topological phase winding and local geometric phase of the band. We measure an overall evolution of 3.1 $\pm$ 0.2 radians for the geometrical phase during the Bloch period, consistent with the expected Zak phase of $\pi$. Our results demonstrate the power of classical analogs of quantum models to directly observe the topological properties of the band structure, and sheds light on the similarities and the differences between quantum and classical topological effects.

Hafnia HfO$_2$ as a Proper Ferroelectric. (arXiv:2305.19446v1 [cond-mat.mtrl-sci])
Aldo Raeliarijaona, R. E. Cohen

We clarify the nature of hafnia as a proper ferroelectric and show that there is a shallow double well involving a single soft polar mode as in well-known classic ferroelectrics. Using symmetry analysis, density-functional theory (DFT) structural optimizations with and without epitaxial strain, and density functional perturbation theory (DFPT), we examine several important possible hafnia structures derived ultimately from the cubic fluorite structure, including baddeleyite (P$2_{1}/c$), tetragonal antiferroelectric P4$_2$nmc, Pbca (nonpolar and brookite), and ferroelectric rhombohedral ($R3m$), Pmn2$_{1}$ and Pca2$_{1}$ structures. The latter is considered to be the most likely ferroelectric phase seen experimentally, and has an antiferroelectric parent with space group Pbcn, with a single unstable polar mode and a shallow double well with a well depth of 24 meV/atom. Strain is not required for switching or other ferroelectric properties, nor is coupling of the soft-mode with any other modes within the ferroelectric Pca2$_{1}$ phase.

Atomically smooth films of CsSb: a chemically robust visible light photocathode. (arXiv:2305.19553v1 [physics.acc-ph])
C. T. Parzyck, C. A. Pennington, W. J. I. DeBenedetti, J. Balajka, E. Echeverria, H. Paik, L. Moreschini, B. D. Faeth, C. Hu, J. K. Nangoi, V. Anil, T. A. Arias, M. A. Hines, D. G. Schlom, A. Galdi, K. M. Shen, J. M. Maxson

Alkali antimonide semiconductor photocathodes provide a promising platform for the generation of high brightness electron beams, which are necessary for the development of cutting-edge probes including x-ray free electron lasers and ultrafast electron diffraction. However, to harness the intrinsic brightness limits in these compounds, extrinsic degrading factors, including surface roughness and contamination, must be overcome. By exploring the growth of CsxSb thin films monitored by in situ electron diffraction, the conditions to reproducibly synthesize atomically smooth films of CsSb on 3C-SiC (100) and graphene coated TiO2 (110) substrates are identified, and detailed structural, morphological, and electronic characterization is presented. These films combine high quantum efficiency in the visible (up to 1.2% at 400 nm), an easily accessible photoemission threshold of 550 nm, low surface roughness (down to 600 pm on a 1 um scale), and a robustness against oxidation up to 15 times greater then Cs3Sb. These properties suggest that CsSb has the potential to operate as an alternative to Cs$_3$Sb in electron source applications where the demands of the vacuum environment might otherwise preclude the use of traditional alkali antimonides.

Interaction-induced Liouvillian skin effect in a fermionic chain with two-body loss. (arXiv:2305.19697v1 [cond-mat.str-el])
Shu Hamanaka, Kazuki Yamamoto, Tsuneya Yoshida

Despite recent intensive research on topological aspects of open quantum systems, effects of strong interactions have not been sufficiently explored. In this paper, we demonstrate that interactions induce the Liouvillian skin effect by analyzing a one-dimensional correlated model with two-body loss. We show that, in the presence of interactions, eigenmodes and eigenvalues of the Liouvillian strongly depend on boundary conditions. Specifically, we find that interactions induce localization of eigenmodes of the Liouvillian around the right edge under open boundary conditions. To characterize the Liouvllian skin effect, we define the topological invariant by using the Liouvillian superoperator. Then, we numerically confirm that the topological invariant captures the Liouvillian skin effect. Furthermore, the presence of the localization of eigenmodes results in the unique dynamics observed only under open boundary conditions: particle accumulation at the right edge in transient dynamics. Our result paves the way to realize topological phenomena in open quantum systems induced by strong interactions.

Sliding and Pinning in Structurally Lubric 2D Material Interfaces. (arXiv:2305.19740v1 [cond-mat.mtrl-sci])
Jin Wang, Ali Khosravi, Andrea Vanossi, Erio Tosatti

A plethora of two-dimensional (2D) materials entered the physics and engineering scene in the last two decades. Their robust, membrane-like sheet permit -- mostly require -- deposition, giving rise to solid-solid dry interfaces whose bodily mobility, pinning, and general tribological properties under shear stress are currently being understood and controlled, experimentally and theoretically. In this Colloquium we use simulation case studies of twisted graphene system as a prototype workhorse tool to demonstrate and discuss the general picture of 2D material interface sliding. First, we highlight the crucial mechanical difference, often overlooked, between small and large incommensurabilities, corresponding e.g., to small and large twist angles in graphene interfaces. In both cases, focusing on flat, structurally lubric, "superlubric" geometries, we elucidate and review the generally separate scaling with area of static friction in pinned states and of kinetic friction during sliding, tangled as they are with the effects of velocity, temperature, load, and defects. Including the role of island boundaries and of elasticity, and corroborating when possible the existing case-by-case results in literature beyond graphene, the overall picture proposed is meant for general 2D material interfaces, that are of importance for the physics and technology of existing and future bilayer and multilayer systems.

Axion Topology in Photonic Crystal Domain Walls. (arXiv:2305.19805v1 [physics.optics])
Chiara Devescovi, Antonio Morales-Pérez, Yoonseok Hwang, Mikel García-Díez, Iñigo Robredo, Juan Luis Mañes, Barry Bradlyn, Aitzol García-Etxarri, Maia G. Vergniory

Axion insulators are 3D magnetic higher-order topological insulators protected by inversion-symmetry that exhibit hinge-localized chiral channels and induce quantized topological magnetoelectric effects. Recent research has suggested that axion insulators may be capable of detecting dark-matter axion-like particles by coupling to their axionic excitations. Beyond its fundamental theoretical interest, designing a photonic AXI offers the potential to enable the development of magnetically-tunable photonic switch devices through the manipulation of the axionic modes and their chiral propagation using external magnetic fields. Motivated by these facts, in this work, we propose a novel approach to induce axionic band topology in gyrotropic 3D Weyl photonic crystals gapped by supercell modulation. To quantize an axionic angle, we create domain-walls across inversion-symmetric photonic crystals, incorporating a phase-obstruction in the supercell modulation of their dielectric elements. This allows us to bind chiral channels on inversion-related hinges, ultimately leading to the realization of an axionic chiral channel of light. Moreover, by controlling the material gyrotropic response, we demonstrate a physically accessible way of manipulating the axionic modes through a small external magnetic bias, which provides an effective topological switch between different 1D chiral photonic fiber configurations. Remarkably, the unidirectional axionic hinge states supported by the photonic axion insulator are buried in a fully connected 3D dielectric structure, thereby being protected from radiation through the electromagnetic continuum. As a result, they are highly suitable for applications in guided-light communication, where the preservation and non-reciprocal propagation of photonic signals are of paramount importance.

Hybrid higher-order skin-topological effect in hyperbolic lattices. (arXiv:2305.19810v1 [cond-mat.mes-hall])
Junsong Sun, Chang-An Li, Shiping Feng, Huaiming Guo

We investigate the non-Hermitian Haldane model on hyperbolic $\{8, 3\}$ and $\{12, 3\}$ lattices, and showcase its intriguing topological properties in the simultaneous presence of non-Hermitian effect and hyperbolic geometry. From bulk descriptions of the system, we calculate the real space non-Hermitian Chern numbers by generalizing the method from its Hermitian counterpart and present corresponding phase diagram of the model. For boundaries, we find that skin-topological modes appear in the range of the bulk energy gap under certain boundary conditions, which can be explained by an effective one-dimensional zigzag chain model mapped from hyperbolic lattice boundary. Remarkably, these skin-topological modes are localized at specific corners of the boundary, constituting a hybrid higher-order skin-topological effect on hyperbolic lattices.

Twistronics of Kekul\'e Graphene: Honeycomb and Kagome Flat Bands. (arXiv:2305.19927v1 [cond-mat.mes-hall])
Michael G. Scheer, Biao Lian

Kekul\'e-O order in graphene, which has recently been realized experimentally, induces Dirac electron masses on the order of $m \sim 100\text{meV}$. We show that twisted bilayer graphene in which one or both layers have Kekul\'e-O order exhibits nontrivial flat electronic bands on honeycomb and kagome lattices. When only one layer has Kekul\'e-O order, there is a parameter regime for which the lowest four bands at charge neutrality form an isolated two-orbital honeycomb lattice model with two flat bands. The bandwidths are minimal at a magic twist angle $\theta \approx 0.7^\circ$ and Dirac mass $m \approx 100\text{meV}$. When both layers have Kekul\'e-O order, there is a large parameter regime around $\theta\approx 1^\circ$ and $m\gtrsim 100\text{meV}$ in which the lowest three valence and conduction bands at charge neutrality each realize isolated kagome lattice models with one flat band, while the next three valence and conduction bands are flat bands on triangular lattices. These flat band systems may provide a new platform for strongly correlated phases of matter.

Dark Matter Detection with Strongly Correlated Topological Materials: Flatband Effect. (arXiv:2305.19967v1 [cond-mat.str-el])
Zhao Huang, Christopher Lane, Sarah E. Grefe, Snehasish Nandy, Benedikt Fauseweh, Silke Paschen, Qimiao Si, Jian-Xin Zhu

Dirac materials have been proposed as a new class of electron-based detectors for light dark-matter (DM) scattering or absorption, with predicted sensitivities far exceeding superconductors and superfluid helium. The superiority of Dirac materials originates from a significantly reduced in-medium dielectric response winning over the suppression of DM scattering owing to the limited phase space at the point-like Fermi surface. Here we propose a new route to enhance significantly the DM detection efficiency via strongly correlated topological semimetals. Specifically, by considering a strongly correlated Weyl semimetal model system, we demonstrate that the strong correlation-induced flatband effects can amplify the coupling and detection sensitivity to light DM particles by expanding the scattering phase space, while maintaining a weak dielectric in-medium response.

Zero-bias conductance peaks at zero applied magnetic field due to stray fields from integrated micromagnets in hybrid nanowire quantum dots. (arXiv:2305.19970v1 [cond-mat.mes-hall])
Y. Jiang, M. Gupta, C. Riggert, M. Pendharkar, C. Dempsey, J.S. Lee, S.D. Harrington, C.J. Palmstrøm, V. S. Pribiag, S.M. Frolov

Many recipes for realizing topological superconductivity rely on broken time-reversal symmetry, which is often attained by applying a substantial external magnetic field. Alternatively, using magnetic materials can offer advantages through low-field operation and design flexibility on the nanoscale. Mechanisms for lifting spin degeneracy include exchange coupling, spin-dependent scattering, spin injection-all requiring direct contact between the bulk or induced superconductor and a magnetic material. Here, we implement locally broken time-reversal symmetry through dipolar coupling from nearby micromagnets to superconductor-semiconductor hybrid nanowire devices. Josephson supercurrent is hysteretic due to micromangets switching. At or around zero external magnetic field, we observe an extended presence of Andreev bound states near zero voltage bias. We also show a zero-bias peak plateau of a non-quantized value. Our findings largely reproduce earlier results where similar effects were presented in the context of topological superconductivity in a homogeneous wire, and attributed to more exotic time-reversal breaking mechanisms [1]. In contrast, our stray field profiles are not designed to create Majorana modes, and our data are compatible with a straightforward interpretation in terms of trivial states in quantum dots. At the same time, the use of micromagnets in hybrid superconductor-semiconductor devices shows promise for future experiments on topological superconductivity.

Measuring irreversibility from learned representations of biological patterns. (arXiv:2305.19983v1 [cond-mat.stat-mech])
Junang Li, Chih-Wei Joshua Liu, Michal Szurek, Nikta Fakhri

Thermodynamic irreversibility is a crucial property of living matter. Irreversible processes maintain spatiotemporally complex structures and functions characteristic of living systems. Robust and general quantification of irreversibility remains a challenging task due to nonlinearities and influences of many coupled degrees of freedom. Here we use deep learning to reveal tractable, low-dimensional representations of patterns in a canonical protein signaling process -- the Rho-GTPase system -- as well as complex Ginzburg-Landau dynamics. We show that our representations recover activity levels and irreversibility trends for a range of patterns. Additionally, we find that our irreversibility estimates serve as a dynamical order parameter, distinguishing stable and chaotic dynamics in these nonlinear systems. Our framework leverages advances in deep learning to quantify the nonequilibrium and nonlinear behavior of complex living processes.

AC Josephson effect in a gate-tunable Cd$_3$As$_2$ nanowire superconducting weak link. (arXiv:2305.19996v1 [cond-mat.supr-con])
Roy Haller, Melissa Osterwalder, Gergő Fülöp, Joost Ridderbos, Minkyung Jung, Christian Schönenberger

Three-dimensional topological Dirac semimetals have recently gained significant attention, since they possess exotic quantum states. When constructing Josephson junctions utilizing these materials as the weak link, the fractional ac Josephson effect emerges in the presence of a topological supercurrent contribution. We investigate the ac Josephson effect in a Dirac semimetal Cd$_3$As$_2$ nanowire using two complementary methods: by probing the radiation spectrum and by measuring Shapiro patterns. With both techniques, we find that conventional supercurrent dominates at all investigated doping levels and that any potentially present topological contribution falls below our detection threshold. The inclusion of thermal noise in a resistively and capacitively shunted junction (RCSJ) model allows us to reproduce the microwave characteristics of the junction. With this refinement, we explain how weak superconducting features can be masked and provide a framework to account for elevated electronic temperatures present in realistic experimental scenarios.

Realization of U(1) Dirac Quantum Spin Liquid in YbZn2GaO5. (arXiv:2305.20040v1 [cond-mat.str-el])
Sijie Xu, Rabindranath Bag, Nicholas E. Sherman, Lalit Yadav, Alexander I. Kolesnikov, Andrey A. Podlesnyak, Joel E. Moore, Sara Haravifard

The emergence of a quantum spin liquid (QSL), a state of matter that can result when electron spins are highly correlated but do not become ordered, has been the subject of a considerable body of research in condensed matter physics. Spin liquid states have been proposed as hosts for high-temperature superconductivity and can host topological properties with potential applications in quantum information science. The excitations of most quantum spin liquids are not conventional spin waves but rather quasiparticles known as spinons, whose existence is well established experimentally only in one-dimensional systems; the unambiguous experimental realization of QSL behavior in higher dimensions remains challenging. Here we investigate the novel compound YbZn2GaO5, which hosts an ideal triangular lattice of effective spin-1/2 moments with no inherent chemical disorder. Thermodynamic and inelastic neutron scattering (INS) measurements performed on high-quality single crystal samples of YbZn2GaO5 exclude the possibility of long-range magnetic ordering down to 60 mK, demonstrate a quadratic power law for the heat capacity and reveal a continuum of magnetic excitations in parts of the Brillouin zone. Both low-temperature thermodynamics and INS spectra suggest that YbZn2GaO5 is a U(1) Dirac QSL with gapless spinon excitations concentrated at certain points in the Brillouin zone, and additional features in INS are also consistent with theoretical expectations for a Dirac QSL on the triangular lattice.

Quantum Monte Carlo study of superconductivity in rhombohedral trilayer graphene under an electric field. (arXiv:2204.06222v2 [cond-mat.str-el] UPDATED)
Huijia Dai, Runyu Ma, Xiao Zhang, Ting Guo, Tianxing Ma

By using the constrained-phase quantum Monte Carlo method, we performed a systematic study of the ground state of the half filled Hubbard model for a trilayer honeycomb lattice. We analyze the effect of the perpendicular electric field on the electronic structure, magnetic property and pairing correlations. It is found that the antiferromagnetism is suppressed by the perpendicular electric field, especially the long-range parts, and the dominant magnetic fluctuations are still antiferromagnetic. The electronic correlation drives a $d+id$ superconducting pairing to be dominant over other pairing patterns among various electric fields and interaction strengths. We also found that the $d+id$ pairing correlation is greatly enhanced as the on-site Coulomb interaction is increased. Our intensive numerical results may unveil the nature of the recently observed superconductivity in rhombohedral trilayer graphene under an electric field.

Fast quantum transfer mediated by topological domain walls. (arXiv:2208.00797v3 [quant-ph] UPDATED)
Juan Zurita, Charles E. Creffield, Gloria Platero

The duration of bidirectional transfer protocols in 1D topological models usually scales exponentially with distance. In this work, we propose transfer protocols in multidomain SSH chains and Creutz ladders that lose the exponential dependence, greatly speeding up the process with respect to their single-domain counterparts, reducing the accumulation of errors and drastically increasing their performance, even in the presence of symmetry-breaking disorder. We also investigate how to harness the localization properties of the Creutz ladder-with two localized modes per domain wall-to choose the two states along the ladder that will be swapped during the transfer protocol, without disturbing the states located in the intermediate walls between them. This provides a 1D network with all-to-all connectivity that can be helpful for quantum information purposes.

Quantum adiabaticity in many-body systems and almost-orthogonality in complementary subspace. (arXiv:2208.02620v2 [quant-ph] UPDATED)
Jyong-Hao Chen, Vadim Cheianov

We study why in quantum many-body systems the adiabatic fidelity and the overlap between the initial state and instantaneous ground states have nearly the same values in many cases. We elaborate on how the problem may be explained by an interplay between the two intrinsic limits of many-body systems: the limit of small values of evolution parameter and the limit of large system size. In the former case, conventional perturbation theory provides a natural explanation. In the latter case, a crucial observation is that pairs of vectors lying in the complementary Hilbert space of the initial state are almost orthogonal. Our general findings are illustrated with a driven Rice-Mele model and a driven interacting Kitaev chain model, two paradigmatic models of driven many-body systems.

Thermal transport in nanoelectronic devices cooled by on-chip magnetic refrigeration. (arXiv:2209.07099v2 [cond-mat.mes-hall] UPDATED)
S. Autti, F. C. Bettsworth, K. Grigoras, D. Gunnarsson, R. P. Haley, A. T. Jones, Yu. A. Pashkin, J. R. Prance, M. Prunnila, M. D. Thompson, D. E. Zmeev

On-chip demagnetization refrigeration has recently emerged as a powerful tool for reaching microkelvin electron temperatures in nanoscale structures. The relative importance of cooling on-chip and off-chip components and the thermal subsystem dynamics are yet to be analyzed. We study a Coulomb blockade thermometer with on-chip copper refrigerant both experimentally and numerically, showing that dynamics in this device are captured by a first-principles model. Our work shows how to simulate thermal dynamics in devices down to microkelvin temperatures, and outlines a recipe for a low-investment platform for quantum technologies and fundamental nanoscience in this novel temperature range.

Photogalvanic effect and second harmonic generation from radio to infrared region in WTe$_2$ monolayer. (arXiv:2302.08103v2 [cond-mat.mes-hall] UPDATED)
Yuan Liu, Zhen-Gang Zhu, Gang Su

Second-order nonlinear optical responses, including photogalvanic effect (PGE) and second harmonic generation (SHG), are important physical phenomena in nonlinear optics. The PGE (SHG) related to linearly and circularly polarized light are called the linear and circular PGE (LPGE and CPGE) [linear and circular SHG (LSHG and CSHG)], respectively. In this work, we use the quantum kinetics under relaxation time approximation to study the dependence of second-order nonlinear optical responses on Fermi level and frequency under different out-of-plane electric fields in WTe$_2$ monolayer from radio to infrared region. We find that the maximum frequency at which the Berry curvature dipole mechanism for the nonlinear Hall effect plays a major role is about 1 THz. In radio and microwave regions, two large peaks of nonlinear conductivities occur when the Fermi level is equal to the energy corresponding to gap-opening points. In terms of frequency, in radio region, LPGE and SHG conductivities maintain a large constant while the CPGE conductivity disappears. In microwave region, LPGE and SHG start to decrease with increasing frequency while the CPGE is large. In 125-300 THz region and in y direction, the presence of DC current without the disturbance of second harmonic current under circularly polarized light may be useful for fabricating new optoelectronic devices. Moreover, we illustrate that when calculating the nonlinear optical responses of practical materials, the theories in the clean limit fail and it is necessary to use a theory that considers scattering effects. We also point out that for materials with femtosecond-scale relaxation times and complex energy band structures, the quantum kinetics is more accurate than the semi-classical Boltzmann equation method. Besides, phenomenological expressions of PGE and SHG are provided.

Anomalous Random Telegraphy Signal in Suspended Graphene with Oxygen Adsorption. (arXiv:2303.01649v2 [cond-mat.mes-hall] UPDATED)
Alexandro de Moraes Nogueira, Afsal Kareekunnan, Masashi Akabori, Hiroshi Mizuta, Manoharan Muruganathan

Graphene is a promising material for sensing applications because of its large specific surface area and low noise. In many applications, graphene will inevitably be in contact with oxygen since it is the second most abundant gas in the atmosphere. Therefore, it is of interest to understand how this gas affects the sensor properties. In this work, the effect of oxygen on the low-frequency noise of suspended graphene is demonstrated. Devices with suspended graphene nanoribbons with a width (W) and length (L) of 200 nm were fabricated. The resistance as a function of time was measured in a vacuum and pure oxygen atmosphere through an ac lock-in method. After signal processing with wavelet denoising and analysis, it is demonstrated that oxygen causes random telegraphy signal (RTS) in the millisecond scale, with an average dwell time of 2.9 milliseconds in the high-resistance state, and 2 milliseconds in the low-resistance state. It is also shown that this RTS occurs only at some periods, which indicates that, upon adsorption, the molecules take some time until they find the most energetically favorable adsorption state. Also, a slow-down in the RTS time constants is observed, which infers that less active sites are available as time goes on because of oxygen adsorption. Therefore, it is very important to consider these effects to guarantee high sensitivity and high durability for graphene-based sensors that will be exposed to oxygen during their lifetime.

Viscous heat backflow and temperature resonances in extreme thermal conductors. (arXiv:2303.12777v3 [cond-mat.mtrl-sci] UPDATED)
Jan Dragašević, Michele Simoncelli

We demonstrate that non-diffusive, fluid-like heat transport, such as heat backflowing from cooler to warmer regions, can be induced, controlled, and amplified in extreme thermal conductors such as graphite and hexagonal boron nitride. We employ the viscous heat equations, i.e. the thermal counterpart of the Navier-Stokes equations in the laminar regime, to show with first-principles quantitative accuracy that a finite thermal viscosity yields steady-state heat vortices, and governs the magnitude of transient temperature waves. Finally, we devise strategies that exploit devices' boundaries and resonance to amplify and control heat hydrodynamics, paving the way for novel experiments and applications in next-generation electronic and phononic technologies.

Breakdown of Conventional Winding Number Calculation in One-Dimensional Lattices with Interactions Beyond Nearest Neighbors. (arXiv:2304.04080v2 [cond-mat.mtrl-sci] UPDATED)
Amir Rajabpoor Alisepahi, Siddhartha Sarkar, Kai Sun, Jihong Ma

Topological indices, such as winding numbers, have been conventionally used to predict the number of topologically protected edge states (TPESs) in topological insulators, a signature of the topological phenomenon called bulk-edge correspondence. In this work, we theoretically and experimentally demonstrate that the number of TPESs at the domain boundary of a Su-Schrieffer-Heeger (SSH) model can be higher than the winding number depending on the strengths of beyond-nearest-neighbors, revealing the breakdown of the winding number prediction. Hence, we resort to the Berry connection to accurately count the number of TPESs in an SSH system with a domain boundary. Moreover, the Berry connection can elucidate wavelengths of the TPESs, which is further confirmed using the Jackiw Rebbi theory. We analytically prove that each of the multiple TPES modes at the domain boundary corresponds to a bulk Dirac cone, asserting the robustness of the Berry connection method, which offers a generalized paradigm for TPES prediction.

Classification of Classical Spin Liquids: Typology and Resulting Landscape. (arXiv:2305.00155v2 [cond-mat.str-el] UPDATED)
Han Yan, Owen Benton, Roderich Moessner, Andriy H. Nevidomskyy

Classical spin liquids (CSL) lack long-range magnetic order and are characterized by an extensive ground state degeneracy. We propose a classification scheme of CSLs based on the structure of the flat bands of their Hamiltonians. Depending on absence or presence of the gap from the flat band, the CSL are classified as algebraic or fragile topological, respectively. Each category is further classified: the algebraic case by the nature of the emergent Gauss's law at the gap-closing point(s), and the fragile topological case by the homotopy of the eigenvector winding around the Brillouin zone. Previously identified instances of CSLs fit snugly into our scheme, which finds a landscape where algebraic CSLs are located at transitions between \fragile topological ones. It also allows us to present a new, simple family of models illustrating that landscape, which hosts both fragile topological and algebraic CSLs, as well as transitions between them.

Magnetostriction-driven muon localisation in an antiferromagnetic oxide. (arXiv:2305.12237v2 [cond-mat.str-el] UPDATED)
Pietro Bonfà, Ifeanyi John Onuorah, Franz Lang, Iurii Timrov, Lorenzo Monacelli, Chennan Wang, Xiao Sun, Oleg Petracic, Giovanni Pizzi, Nicola Marzari, Stephen J. Blundell, Roberto De Renzi

Magnetostriction drives a rhombohedral distortion in the cubic rock salt antiferromagnet MnO at the N\'eel temperature $T_{N}=118$ K. As an unexpected consequence we show that this distortion acts to localize the site of an implanted muon due to the accompanying redistribution of electron density. This lifts the degeneracy between equivalent sites, resulting in a single observed muon precession frequency. Above $T_{N}$, the muon instead becomes delocalized around a network of equivalent sites. Our first-principles simulations based on Hubbard-corrected density-functional theory and molecular dynamics are consistent with our experimental data and help to resolve a long-standing puzzle regarding muon data on MnO, as well as having wider applicability to other magnetic oxides.

Bilayer two-orbital model of La$_3$Ni$_2$O$_7$ under pressure. (arXiv:2305.15564v2 [cond-mat.supr-con] UPDATED)
Zhihui Luo, Xunwu Hu, Meng Wang, Wéi Wú, Dao-Xin Yao

The newly discovered Ruddlesden-Popper bilayer La$_3$Ni$_2$O$_7$ reaches an remarkable superconducting transition temperature $T_c$ = 80 K under a pressure of above 14 GPa. Here we propose a minimal bilayer two-orbital model of the high-pressure phase of La$_3$Ni$_2$O$_7$. Our model is constructed with the Ni-3d$_{x^2-y^2}$, 3d$_{3z^2-r^2}$ orbitals by using Wannier downfolding of the density functional theory calculations, which captures the key ingredients of the material, such as band structure and Fermi surface topology. There are two electron pockets $\alpha$, $\beta$ and one hole pocket $\gamma$ on the Fermi surface, in which the $\alpha$, $\beta$ pockets show mixing of two orbitals, while the $\gamma$ pocket is associated with Ni-d$_{3z^2-r^2}$ orbital. The RPA spin susceptibility reveals a magnetic enhancement associating to the d$_{3z^2-r^2}$ state. A higher energy model with O-p orbitals is also provided for further study.

Anisotropic exciton polariton pairs as a platform for PT-symmetric non-Hermitian physics. (arXiv:2305.17472v2 [cond-mat.mes-hall] UPDATED)
Devarshi Chakrabarty, Avijit Dhara, Pritam Das, Kritika Ghosh, Ayan Roy Chaudhuri, Sajal Dhara

Non-Hermitian systems with parity-time (PT) symmetry have been realized using optical constructs in the classical domain, leading to a plethora of non-intuitive phenomena. However, PT-symmetry in purely quantum non-Hermitian systems like microcavity exciton-polaritons has not been realized so far. Here we show how a pair of nearly orthogonal sets of anisotropic exciton-polaritons can offer a versatile platform for realizing multiple spectral degeneracies called Exceptional Points (EPs) and propose a roadmap to achieve a PT-symmetric system. Polarization-tunable coupling strength creates one class of EPs, while Voigt EPs are observed for specific orientations where splitting of polariton modes due to birefringence is compensated by Transverse Electric (TE) -Transverse Magnetic (TM) mode splitting. Thus, paired sets of polarized anisotropic microcavity exciton-polaritons can offer a promising platform not only for fundamental research in non-Hermitian quantum physics and topological polaritons, but also, we propose that it will be critical for realizing zero threshold lasers.

Generalized Charges, Part II: Non-Invertible Symmetries and the Symmetry TFT. (arXiv:2305.17159v1 [hep-th] CROSS LISTED)
Lakshya Bhardwaj, Sakura Schafer-Nameki

Consider a d-dimensional quantum field theory (QFT) $\mathfrak{T}$, with a generalized symmetry $\mathcal{S}$, which may or may not be invertible. We study the action of $\mathcal{S}$ on generalized or $q$-charges, i.e. $q$-dimensional operators. The main result of this paper is that $q$-charges are characterized in terms of the topological defects of the Symmetry Topological Field Theory (SymTFT) of $\mathcal{S}$, also known as the ``Sandwich Construction''. The SymTFT is a $(d+1)$-dimensional topological field theory, which encodes the symmetry $\mathcal{S}$ and the physical theory in terms of its boundary conditions. Our proposal applies quite generally to any finite symmetry $\mathcal{S}$, including non-invertible, categorical symmetries. Mathematically, the topological defects of the SymTFT form the Drinfeld Center of the symmetry category $\mathcal{S}$. Applied to invertible symmetries, we recover the result of Part I of this series of papers. After providing general arguments for the identification of $q$-charges with the topological defects of the SymTFT, we develop this program in detail for QFTs in 2d (for general fusion category symmetries) and 3d (for fusion 2-category symmetries).

Found 5 papers in prb
Date of feed: Thu, 01 Jun 2023 03:17:09 GMT

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Anomalous valley Hall effect induced by mirror symmetry breaking in transition metal dichalcogenides
Shilei Ji, Ruijia Yao, Chuye Quan, Jianping Yang, Fabio Caruso, and Xing'ao Li
Author(s): Shilei Ji, Ruijia Yao, Chuye Quan, Jianping Yang, Fabio Caruso, and Xing'ao Li

The control of the valley degree of freedom in Bloch electrons has opened up new avenues for information processing. The synthesis of ferrovalley materials, however, has been limited due to the stringent requirements for breaking both time and space inversion symmetries. To address this challenge, w…

[Phys. Rev. B 107, 174434] Published Wed May 31, 2023

Electronic density of states of a $U(1)$ quantum spin liquid with spinon Fermi surface. I. Orbital magnetic field effects
Wen-Yu He and Patrick A. Lee
Author(s): Wen-Yu He and Patrick A. Lee

The authors study the orbital magnetic field induced Landau quantization of a quantum spin liquid with spinon Fermi surface. In the electronic density of states of the quantum spin liquid, the Landau quantization is found to induce a set of band-edge steps, band-edge resonance peaks, or in-gap bound states when the gauge-field fluctuations are negligible, weak, or strong, respectively. The results indicate that the Landau quantization of the spinon Fermi surface can be detected through scanning tunneling microscope measurements.

[Phys. Rev. B 107, 195155] Published Wed May 31, 2023

Separating anisotropic and isotropic friction between atomic force microscope tips and atomically flat surfaces
Mengzhou Liao, Paolo Nicolini, and Tomas Polcar
Author(s): Mengzhou Liao, Paolo Nicolini, and Tomas Polcar

Layered materials are the most important class of solid lubricants. Friction on their surfaces has complex origins. Most experimental methods so far only give total friction force and cannot separate contributions from different origins. Here, we report a method to separate anisotropic and isotropic…

[Phys. Rev. B 107, 195442] Published Wed May 31, 2023

Non-Bloch topological phases in a Hermitian system
Kaiye Shi, Mingsheng Tian, Feng-Xiao Sun, and Wei Zhang
Author(s): Kaiye Shi, Mingsheng Tian, Feng-Xiao Sun, and Wei Zhang

The search for novel topological states of matter remains to be a research focus in the past several decades. While a topology theory based on Bloch bands is thoroughly investigated in systems with finite-range hopping, mostly in the context of condensed matter physics, here we study a generalized o…

[Phys. Rev. B 107, 205154] Published Wed May 31, 2023

Interference effects in polarization-controlled Rayleigh scattering in twisted bilayer graphene
Disha Arora, Deepanshu Aggarwal, Sankalpa Ghosh, and Rohit Narula
Author(s): Disha Arora, Deepanshu Aggarwal, Sankalpa Ghosh, and Rohit Narula

We calculate the polarization-controlled Rayleigh scattering response of twisted bilayer graphene (tBLG) based on the continuum electronic band model developed by Bistritzer and MacDonald while considering its refinements which address the effects of structural corrugation, doping-dependent Hartree …

[Phys. Rev. B 107, 205423] Published Wed May 31, 2023

Found 5 papers in prl
Date of feed: Thu, 01 Jun 2023 03:17:08 GMT

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Oscillating Solitons and ac Josephson Effect in Ferromagnetic Bose-Bose Mixtures
S. Bresolin, A. Roy, G. Ferrari, A. Recati, and N. Pavloff
Author(s): S. Bresolin, A. Roy, G. Ferrari, A. Recati, and N. Pavloff

Close to the demixing transition, the degree of freedom associated with relative density fluctuations of a two-component Bose-Einstein condensate is described by a nondissipative Landau-Lifshitz equation. In the quasi-one-dimensional weakly immiscible case, this mapping surprisingly predicts that a …

[Phys. Rev. Lett. 130, 220403] Published Wed May 31, 2023

Analytic Approach to Light Dark Matter Propagation
Christopher V. Cappiello
Author(s): Christopher V. Cappiello

If dark matter interacts too strongly with nuclei, it could be slowed to undetectable speeds in Earth’s crust or atmosphere before reaching a detector. For sub-GeV dark matter, approximations appropriate for heavier dark matter fail, necessitating the use of computationally expensive simulations. We…

[Phys. Rev. Lett. 130, 221001] Published Wed May 31, 2023

Partition Function for a Volume of Space
Ted Jacobson and Manus R. Visser
Author(s): Ted Jacobson and Manus R. Visser

A new calculation shows that any region of space with the topology of a ball has a standard Bekenstein-Hawking entropy.

[Phys. Rev. Lett. 130, 221501] Published Wed May 31, 2023

Quantum Discord and Steering in Top Quarks at the LHC
Yoav Afik and Juan Ramón Muñoz de Nova
Author(s): Yoav Afik and Juan Ramón Muñoz de Nova

Top quarks have been recently shown to be a promising system to study quantum information at the highest-energy scale available. The current lines of research mostly discuss topics such as entanglement, Bell nonlocality or quantum tomography. Here, we provide the full picture of quantum correlations…

[Phys. Rev. Lett. 130, 221801] Published Wed May 31, 2023

Hexagonal Close-Packed Polar-Skyrmion Lattice in Ultrathin Ferroelectric ${\mathrm{PbTiO}}_{3}$ Films
Shuai Yuan, Zuhuang Chen, Sergei Prokhorenko, Yousra Nahas, Laurent Bellaiche, Chenhan Liu, Bin Xu, Lang Chen, Sujit Das, and Lane W. Martin
Author(s): Shuai Yuan, Zuhuang Chen, Sergei Prokhorenko, Yousra Nahas, Laurent Bellaiche, Chenhan Liu, Bin Xu, Lang Chen, Sujit Das, and Lane W. Martin

Polar skyrmions are topologically stable, swirling polarization textures with particlelike characteristics, which hold promise for next-generation, nanoscale logic and memory. However, the understanding of how to create ordered polar skyrmion lattice structures and how such structures respond to app…

[Phys. Rev. Lett. 130, 226801] Published Wed May 31, 2023

Found 1 papers in pr_res
Date of feed: Thu, 01 Jun 2023 03:17:08 GMT

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Designing exceptional-point-based graphs yielding topologically guaranteed quantum search
Quancheng Liu, David A. Kessler, and Eli Barkai
Author(s): Quancheng Liu, David A. Kessler, and Eli Barkai

Quantum walks underlie an important class of quantum computing algorithms, and represent promising approaches in various simulations and practical applications. Here we design stroboscopically monitored quantum walks and their subsequent graphs that can naturally boost target searches. We show how t…

[Phys. Rev. Research 5, 023141] Published Wed May 31, 2023

Found 1 papers in scipost

Search terms: (topolog[a-z]+)|(graphit[a-z]+)|(rhombohedr[a-z]+)|(graphe[a-z]+)|(chalcog[a-z]+)|(landau)|(weyl)|(dirac)|(STM)|(scan[a-z]+ tunne[a-z]+ micr[a-z]+)|(scan[a-z]+ tunne[a-z]+ spectr[a-z]+)|(scan[a-z]+ prob[a-z]+ micr[a-z]+)|(MoS.+\d+|MoS\d+)|(MoSe.+\d+|MoSe\d+)|(MoTe.+\d+|MoTe\d+)|(WS.+\d+|WS\d+)|(WSe.+\d+|WSe\d+)|(WTe.+\d+|WTe\d+)|(Bi\d+Rh\d+I\d+|Bi.+\d+.+Rh.+\d+.+I.+\d+.+)|(BiTeI)|(BiTeBr)|(BiTeCl)|(ZrTe5|ZrTe.+5)|(Pt2HgSe3|Pt.+2HgSe.+3)|(jacuting[a-z]+)

Restoration of the non-Hermitian bulk-boundary correspondence via topological amplification, by Matteo Brunelli, Clara C. Wanjura, Andreas Nunnenkamp
< author missing >
Submitted on 2023-05-31, refereeing deadline 2023-07-06.