Found 30 papers in cond-mat
Date of feed: Thu, 03 Aug 2023 00:30:00 GMT

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Lieb-Schultz-Mattis anomalies and web of dualities induced by gauging in quantum spin chains. (arXiv:2308.00743v1 [cond-mat.str-el])
Ömer M. Aksoy, Christopher Mudry, Akira Furusaki, Apoorv Tiwari

Lieb-Schultz-Mattis (LSM) theorems impose non-perturbative constraints on the zero-temperature phase diagrams of quantum lattice Hamiltonians (always assumed to be local in this paper). LSM theorems have recently been interpreted as the lattice counterparts to mixed 't Hooft anomalies in quantum field theories that arise from a combination of crystalline and global internal symmetry groups. Accordingly, LSM theorems have been reinterpreted as LSM anomalies. In this work, we provide a systematic diagnostic for LSM anomalies in one spatial dimension. We show that gauging subgroups of the global internal symmetry group of a quantum lattice model obeying an LSM anomaly delivers a dual quantum lattice Hamiltonian such that its internal and crystalline symmetries mix non-trivially through a group extension. This mixing of crystalline and internal symmetries after gauging is a direct consequence of the LSM anomaly, i.e., it can be used as a diagnostic of an LSM anomaly. We exemplify this procedure for a quantum spin-1/2 chain obeying an LSM anomaly resulting from combining a global internal $\mathbb{Z}^{\,}_{2}\times\mathbb{Z}^{\,}_{2}$ symmetry with translation or reflection symmetry. We establish a triality of models by gauging a $\mathbb{Z}^{\,}_{2}\subset\mathbb{Z}^{\,}_{2}\times\mathbb{Z}^{\,}_{2}$ symmetry in two ways, one of which amounts to performing a Kramers-Wannier duality, while the other implements a Jordan-Wigner duality. We discuss the mapping of the phase diagram of the quantum spin-1/2 $XYZ$ chains under such a triality. We show that the deconfined quantum critical transitions between Neel and dimer orders are mapped to either topological or conventional Landau-Ginzburg transitions.

Quadratic Dirac fermions and the competition of ordered states in twisted bilayer graphene. (arXiv:2308.00748v1 [cond-mat.str-el])
Julian Ingham, Tommy Li, Mathias S. Scheurer, Harley D. Scammell

Magic-angle twisted bilayer graphene (TBG) exhibits a captivating phase diagram as a function of doping, featuring superconductivity and a variety of insulating and magnetic states. The bands host Dirac fermions with a reduced Fermi velocity; experiments have shown that the Dirac dispersion reappears near integer fillings of the moir\'e unit cell -- referred to as the $\textit{Dirac revival}$ phenomenon. The reduced velocity of these Dirac states leads us to propose a scenario in which the Dirac fermions possess an approximately quadratic dispersion. The quadratic momentum dependence and particle-hole degeneracy at the Dirac point results in a logarithmic enhancement of interaction effects, which does not appear for a linear dispersion. The resulting non-trivial renormalisation group (RG) flow naturally produces the qualitative phase diagram as a function of doping -- with nematic and insulating states near integer fillings, which give way to superconducting states past a critical relative doping. The RG method further produces different results to strong-coupling Hartree-Fock treatments: producing T-IVC insulating states for repulsive interactions, explaining the results of very recent STM experiments, alongside nodal $A_2$ superconductivity near half-filling, whose properties explain puzzles in tunnelling studies of the superconducting state. The model explains a diverse range of additional experimental observations, unifying many aspects of the phase diagram of TBG.

Manipulating Topological Quantum Phase Transitions of Kitaev's Quantum Spin Liquids with Electric Fields. (arXiv:2308.00760v1 [cond-mat.str-el])
Pureum Noh, Kyusung Hwang, Eun-Gook Moon

Highly entangled excitations such as Majorana fermions of Kitaev quantum spin liquids have been proposed to be utilized for future quantum science and technology, and a deeper understanding of such excitations has been strongly desired. Here we demonstrate that Majorana fermion's mass and associated topological quantum phase transitions in the Kitaev quantum spin liquids may be manipulated by using electric fields in sharp contrast to the common belief that an insulator is inert under weak electric fields due to charge energy gaps. Using general symmetry analysis with perturbation and exact diagonalization, we uncover the universal phase diagrams with electric and magnetic fields. We also provide distinctive experimental signatures to identify Kitaev quantum spin liquids with electric fields, especially in connection with the candidate materials such as $\alpha$-RuCl3.

Lack of near-sightedness principle in non-Hermitian systems. (arXiv:2308.00776v1 [cond-mat.mes-hall])
Helene Spring, Viktor Könye, Anton R. Akhmerov, Ion Cosma Fulga

The non-Hermitian skin effect is a phenomenon in which an extensive number of states accumulates at the boundaries of a system. It has been associated to nontrivial topology, with nonzero bulk invariants predicting its appearance and its position in real space. Here we demonstrate that the non-Hermitian skin effect is not a topological phenomenon in general: when translation symmetry is broken by a single non-Hermitian impurity, skin modes are depleted at the boundary and accumulate at the impurity site, without changing any bulk invariant. This may occur even for a fully Hermitian bulk.

Strong-coupling phases of trions and excitons in electron-hole bilayers at commensurate densities. (arXiv:2308.00825v1 [cond-mat.str-el])
David D. Dai, Liang Fu

We introduce density imbalanced electron-hole bilayers at a commensurate 2 : 1 density ratio as a platform for realizing novel phases involving electrons, excitons and trions. Three length scales are identified which characterize the interplay between kinetic energy, intralayer repulsion, and interlayer attraction. By a combination of theoretical analysis and numerical calculation, we find a variety of strong-coupling phases in different parameter regions, including quantum crystals of electrons, excitons, and trions. We also propose an "excitonic supersolid" phase that features electron crystallization and exciton superfluidity simultaneously. The material realization and experimental signature of these phases are discussed in the context of semiconductor transition metal dichalcogenide bilayers.

Interaction-driven (quasi-) insulating ground states of gapped electron-doped bilayer graphene. (arXiv:2308.00827v1 [cond-mat.str-el])
Anna M. Seiler, Martin Statz, Isabell Weimer, Nils Jacobsen, Kenji Watanabe, Takashi Taniguchi, Zhiyu Dong, Leonid S. Levitov, R. Thomas Weitz

Bernal bilayer graphene has recently been discovered to exhibit a wide range of unique ordered phases resulting from interaction-driven effects and encompassing spin and valley magnetism, correlated insulators, correlated metals, and superconductivity. This letter reports on a novel family of correlated phases characterized by spin and valley ordering, observed in electron-doped bilayer graphene. The novel correlated phases demonstrate an intriguing non-linear current-bias behavior at ultralow currents that is sensitive to the onset of the phases and is accompanied by an insulating temperature dependence, providing strong evidence for the presence of unconventional charge carrying degrees of freedom originating from ordering. These characteristics cannot be solely attributed to any of the previously reported phases, and are qualitatively different from the behavior seen previously on the hole-doped side. Instead, our observations align with the presence of charge- or spin-density-waves state that open a gap on a portion of the Fermi surface or fully gapped Wigner crystals. The resulting new phases, quasi-insulators in which part of the Fermi surface remains intact or valley-polarized and valley-unpolarized Wigner crystals, coexist with previously known Stoner phases, resulting in an exceptionally intricate phase diagram.

Giant superconducting diode effect in ion-beam patterned Sn-based superconductor nanowire / topological Dirac semimetal planar heterostructures. (arXiv:2308.00893v1 [cond-mat.supr-con])
Keita Ishihara, Le Duc Anh, Tomoki Hotta, Kohdai Inagaki, Masaki Kobayashi, Masaaki Tanaka

Superconductor/topological material heterostructures are intensively studied as a platform for topological superconductivity and Majorana physics. However, the high cost of nanofabrication and the difficulty of preparing high-quality interfaces between the two dissimilar materials are common obstacles that hinder the observation of intrinsic physics and the realisation of scalable topological devices and circuits. Here, we demonstrate an innovative method to directly draw nanoscale superconducting beta-tin (beta-Sn) patterns of any shape in the plane of a topological Dirac semimetal (TDS) alpha-tin (alpha-Sn) thin film by irradiating a focused ion beam (FIB). We utilise the property that alpha-Sn undergoes a phase transition to superconducting beta-Sn upon heating by FIB. In beta-Sn nanowires embedded in a TDS alpha-Sn thin film, we observe giant non-reciprocal superconducting transport, where the critical current changes by 69% upon reversing the current direction. The superconducting diode rectification ratio reaches a maximum when the magnetic field is applied parallel to the current, distinguishing itself from all the previous reports. Moreover, it oscillates between alternate signs with increasing magnetic field strength. The angular dependence of the rectification ratio on the magnetic field and current directions is similar to that of the chiral anomaly effect in TDS alpha-Sn, suggesting that the non-reciprocal superconducting transport may occur at the beta-Sn/alpha-Sn interfaces. The ion-beam patterned Sn-based superconductor/TDS planar structures thus show promise as a universal platform for investigating novel quantum physics and devices based on topological superconducting circuits of any shape.

Selectable diffusion direction with topologically protected edge modes. (arXiv:2308.00902v1 [cond-mat.mes-hall])
Keita Funayama, Jun Hirotani, Atsushi Miura, Hiroya Tanaka

Topological insulators provide great potentials to control diffusion phenomena as well as waves. Here, we show that the direction of thermal diffusion can be selected by the contributions of the topologically protected edge modes via the quantum spin Hall effect in a honeycomb-shaped structure. We demonstrate that when we set our structure to the temperature corresponding to the type of edge mode, the direction of thermal diffusion can be tuned. Moreover, this diffusion system is found to be immune to defects owing to the robustness of topological states. Our work points to exciting new avenues for controlling diffusion phenomena.

Searching for Majorana quasiparticles at vortex cores in iron-based superconductors. (arXiv:2308.00930v1 [cond-mat.supr-con])
Tadashi Machida, Tetsuo Hanaguri

The unambiguous detection of the Majorana zero mode (MZM), which is essential for future topological quantum computing, has been a challenge in recent condensed matter experiments. The MZM is expected to emerge at the vortex core of topological superconductors as a zero-energy vortex bound state (ZVBS), amenable to detection using scanning tunneling microscopy/spectroscopy (STM/STS). However, the typical energy resolution of STM/STS has made it challenging to distinguish the MZM from the low-lying trivial vortex bound states. Here, we review the recent high-energy-resolution STM/STS experiments on the vortex cores of Fe(Se,Te), where the MZM is expected to emerge, and the energy of the lowest trivial bound states is reasonably high. Tunneling spectra taken at the vortex cores exhibit a ZVBS well below any possible trivial state, suggesting its MZM origin. However, it should be noted that ZVBS is a necessary but not sufficient condition for the MZM; a qualitative feature unique to the MZM needs to be explored. We discuss the current status and issues in the pursuit of such Majorananess, namely the level sequence of the vortex bound states and the conductance plateau of the ZVBS. We also argue for future experiments to confirm the Majorananess, such as the detection of the doubling of the shot noise intensity and spin polarization of the MZM.

Direction-sensitive graphene flow sensor. (arXiv:2308.00965v1 [])
P. Kaźmierczak, J. Binder, K. Boryczko, T. Ciuk, W. Strupiński, R. Stępniewski, A. Wysmołek

Graphene flow sensors hold great prospects for applications, but also encounter many difficulties, such as unwanted electrochemical phenomena, low measurable signal and limited dependence on the flow direction. This study proposes a novel approach allowing for the detection of a flow direction-dependent electric signal in aqueous solutions of salts, acids and bases. The key element in the proposed solution is the use of a reference electrode which allows external gating of the graphene structure. Using external gating enables to enhance substantially the amplitude of the flow-generated signal. Simultaneous measurement of the reference electrode current allows us to recover a flow-direction-sensitive component of the flow-induced voltage in graphene. The obtained results are discussed in terms of the Coulomb interaction and other phenomena which can be present at the interface of graphene with the aqueous solution.

Quantized Thermal Hall Conductance and the Topological Phase Diagram of a Superconducting Bismuth Bilayer. (arXiv:2308.01021v1 [cond-mat.mes-hall])
Szczepan Głodzik, Nicholas Sedlmayr

Two dimensional topological superconductors with chiral edge modes are predicted to posses a quantized thermal Hall effect, exactly half that for chiral topological insulators, which is proportional to the Chern number. However not much work has been done in identifying this in the standard models in the literature. Here we introduce a model based on a proximity induced superconducting Bismuth bilayer, to directly calculate the thermal Hall conductance based on the lattice model. This model serves as a demonstration of the state of the art possible in such a calculation, as well as introducing an interesting paradigmatic topological superconductor with a rich phase diagram. We demonstrate the quantized thermal Hall plateaus in several different topological phases, and compare this to numerical calculations of the Chern number, as well as analytical calculations of the Chern number's parity invariant. We demonstrate that it is possible to get a reasonable topological phase diagram from the quantized thermal Hall calculations.

Magnetization control of the nematicity direction and nodal points in a superconducting doped topological insulator. (arXiv:2308.01081v1 [cond-mat.supr-con])
D. A. Khokhlov, R. S. Akzyanov, A. V. Kapranov

We study the effects of magnetization on the properties of the doped topological insulator with nematic superconductivity. We found that the direction of the in-plane magnetization fixes the direction of the nematicity in the system. The chiral state is more favorable than the nematic state for large values of out-of-plane magnetization. Overall, the critical temperature of the nematic state is resilient against magnetization. We explore the spectrum of the system with the pinned direction of the nematic order parameter $\Delta_{y}$ in details. Without magnetization, there is a full gap in the spectrum. At strong enough out-of-plane $m_z$ or orthogonal in-plane $m_x$ magnetization, the spectrum is closed at the nodal points that are split by the magnetization. Flat Majorana surface states connect such split bulk nodal points. Parallel magnetization $m_y$ lifts nodal points and opens a full gap in the spectrum. We discuss relevant experiments and propose experimental verifications of our theory.

Minimal effective model and possible high-$T_{c}$ mechanism for superconductivity of La$_{3}$Ni$_{2}$O$_{7}$ under high pressure. (arXiv:2308.01176v1 [cond-mat.supr-con])
Yi-feng Yang, Guang-Ming Zhang, Fu-Chun Zhang

The recent discovery of high-$T_{c}$ superconductivity in bilayer nickelate La$_{3}$Ni$_{2}$O$_{7}$ under high pressure has stimulated great interest concerning its pairing mechanism. We argue that the weak coupling model from the almost fully-filled $d_{z^{2}}$ bonding band cannot give rise to its high $T_{c}$, and thus propose a strong coupling model based on local inter-layer spin singlets of Ni-$d_{z^{2}}$ electrons due to their strong on-site Coulomb repulsion. This leads to a minimal effective model that contains local pairing of $d_{z^{2}}$ electrons and a considerable hybridization with near quarter-filled itinerant $d_{x^{2}-y^{2}}$ electrons on nearest-neighbor sites. The strong coupling between two components provides a composite scenario to achieve high-$T_{c}$ superconductivity. Our theory highlights the importance of the bilayer structure of superconducting La$_{3}$Ni$_{2}$O$_{7}$ and points out a potential route for the exploration of more high-$T_{c}$ superconductors.

Universal conductance fluctuations in a MnBi$_2$Te$_4$ thin film. (arXiv:2308.01183v1 [cond-mat.mes-hall])
Molly P. Andersen, Evgeny Mikheev, Ilan T. Rosen, Lixuan Tai, Peng Zhang, Kang L. Wang, Marc A. Kastner, David Goldhaber-Gordon

Quantum coherence of electrons can produce striking behaviors in mesoscopic conductors, including weak localization and the Aharonov-Bohm effect. Although magnetic order can also strongly affect transport, the combination of coherence and magnetic order has been largely unexplored. Here, we examine quantum coherence-driven universal conductance fluctuations in the antiferromagnetic, canted antiferromagnetic, and ferromagnetic phases of a thin film of the topological material MnBi$_2$Te$_4$. In each magnetic phase we extract a charge carrier phase coherence length of about 100 nm. The conductance magnetofingerprint is repeatable when sweeping applied magnetic field within one magnetic phase, but changes when the applied magnetic field crosses the antiferromagnetic/canted antiferromagnetic magnetic phase boundary. Surprisingly, in the antiferromagnetic and canted antiferromagnetic phase, but not in the ferromagnetic phase, the magnetofingerprint depends on the direction of the field sweep. To explain these observations, we suggest that conductance fluctuation measurements are sensitive to the motion and nucleation of magnetic domain walls in MnBi$_2$Te$_4$.

Comprehensive investigation of Quantum Oscillations in Semimetal Using an ac Composite Magnetoelectric Technique with Ultrahigh Sensitivity. (arXiv:2308.01212v1 [cond-mat.str-el])
Long Zhang, Tianyang Wang, Yugang Zhang, Shuang Liu, Yuping Sun, Xiaoyuan Zhou, Young Sun, Mingquan He, Aifeng Wang, Xuan Luo, Yisheng Chai

Quantum oscillation (QO), a physical phenomenon that reflects the characteristics of the Fermi surface and transport fermions, has been extensively observed in metals and semimetals through various approaches, like magnetostriction, magnetization, resistivity, and thermoelectric power. However, only some allowed oscillation frequencies can be revealed by each individual method, particularly in semimetals with intricate Fermi pockets and associated magnetic breakdown phenomena. In this paper, we present the application of an ac composite magnetoelectric (ME) technique to measure the QOs of a topological nodal-line semimetal, ZrSiS, which possesses six fundamental QO frequencies. By employing the ME technique with a maximum magnetic field of 13 T and a minimum temperature of 2 K, we are able to capture all the fundamental frequencies and most of the permissible magnetic breakdown frequencies. In comparison, some of the frequencies were missing in the aforementioned four methods under identical measurement conditions. Remarkably, a series of magnetic breakdown frequencies around 8000 T were revealed even in a magnetic field as low as 7.5 T. These findings highlight the ME technique as an ultrahigh-sensitive tool for studying Dirac Fermions and other topological semimetals with complex Fermi surfaces.

Broad Band Mott Localization is all you need for Hot Superconductivity: Atom Mott Insulator Theory for Cu-Pb Apatite. (arXiv:2308.01307v1 [cond-mat.supr-con])
G. Baskaran

A hypothetical non-dimerized Cu chain in equilibrium is a spin-\half atom Mott insulator (AMI), eventhough its band width is high ~ 10 eV. This RVB reservoir has a large exchange coupling J ~ 2 eV. This idea of, \textit{broad band Mott localization} was used by us in our earlier works, including prediction of high Tc superconductivity in doped graphene, silicene and a theory for hot superconductivity reported in Ag-Au nanostructures (TP 2008). In the present work we identify possible random AMI subsystems in Cu-Pb Apatite and develop a model for reported hot superconductivity (LKK 2023). In apatite structure, network of interstitial columnar spaces run parallel to c-axis and ab-plane. They accomodate excess copper, as neutral Cu atom clusters, chains and planar segments. They are our emergent AMI's. Electron transfer from AMI's to insulating host, generates strong local superconducting correlation, via phyics of doped Mott insulator. Josephson coupling between doped AMI's, establishes hot superconductivity. A major Challenge to superconducting order in real material is competing insulating phases - valence bond solid (spin-Peirels)-lattice distortions etc. AMI theory points to ways of making the \textit{elusive superconductivity} palpable. We recommend exploration of hot superconductivity in the rich world of minerals and insulators, via metal atom inclusion.

Neglected $U(1)$ phase in the Schroedinger representation of quantum mechanics and particle number conserving formalisms for superconductivity. (arXiv:2211.08759v3 [cond-mat.supr-con] UPDATED)
Hiroyasu Koizumi

Superconductivity is reformulated as a phenomenon in which a stable velocity field is created by a $U(1)$ phase neglected by Dirac in the Schroedinger representation of quantum mechanics. The neglected phase gives rise to a $U(1)$ gauge field expressed as the Berry connection from many-body wave functions. The inclusion of this gauge field transforms the standard particle-number non-conserving formalism of superconductivity to a particle-number conserving one with many results of the former unaltered. In other words, the new formalism indicates that the current standard one is an approximation that effectively takes into account this neglected $U(1)$ gauge field by employing the particle-number non-conserving formalism. Since the standard and new formalisms are physically different, conflicting results are predicted in some cases. We reexamine the Josephson relation and show that a capacitance contribution of the Josephson junction to the $U(1)$ phase is missing in the standard formalism, and inclusion of it indicates that the standard theory actually does one agree with the experiment while the new one does. It is also shown that the dissipative quantum phase transition in Josephson junctions predicted in the standard theory does not exit in the new one in accordance with the recent experimental result.

Unifying Constructions of Non-Invertible Symmetries. (arXiv:2212.06159v2 [hep-th] UPDATED)
Lakshya Bhardwaj, Sakura Schafer-Nameki, Apoorv Tiwari

In the past year several constructions of non-invertible symmetries in Quantum Field Theory in $d\geq 3$ have appeared. In this paper we provide a unified perspective on these constructions. Central to this framework are so-called theta defects, which generalize the notion of theta-angles, and allow the construction of universal and non-universal topological symmetry defects. We complement this physical analysis by proposing a mathematical framework (based on higher-fusion categories) that converts the physical construction of non-invertible symmetries into a concrete computational scheme.

Mixed singlet-triplet superconducting state within the moir\'e $t$-$J$-$U$ model as applied to the description of twisted WSe$_2$ bilayer. (arXiv:2302.13841v2 [cond-mat.str-el] UPDATED)
M. Zegrodnik, A. Biborski

We analyze an analog of the $t$-$J$-$U$ model as applied to the description of a single moir\'e flat band of twisted WSe$_2$ bilayer. To take into account the correlation effects induced by a significant strength of the Coulomb repulsion, we use the Gutzwiller approach and compare it with the results obtained by the Hartree-Fock method. We discuss in detail the graduate appearance of a two dome structure of the superconducting state in the phase diagram by systematically increasing the Coulomb repulsion integral, $U$. The two superconducting domes residing on both sides of a Mott insulating state can be reproduced for a realistic parameter range in agreement with the available experimental data. According to our analysis the paired state has a highly unconventional character with a mixed $d+id$ (singlet) and $p-ip$ (triplet) symmetry. Both components of the mixed paired state are of comparable amplitudes. However, as shown here, a transition between pure singlet and pure triplet pairing should be possible in the considered system by tuning the gate voltage, which controls the magnitude of the valley-dependent spin-splitting in the system.

Bounds to electron spin qubit variability for scalable CMOS architectures. (arXiv:2303.14864v2 [quant-ph] UPDATED)
Jesús D. Cifuentes, Tuomo Tanttu, Will Gilbert, Jonathan Y. Huang, Ensar Vahapoglu, Ross C. C. Leon, Santiago Serrano, Dennis Otter, Daniel Dunmore, Philip Y. Mai, Frédéric Schlattner, MengKe Feng, Kohei Itoh, Nikolay Abrosimov, Hans-Joachim Pohl, Michael Thewalt, Arne Laucht, Chih Hwan Yang, Christopher C. Escott, Wee Han Lim, Fay E. Hudson, Rajib Rahman, Andrew S. Dzurak, Andre Saraiva

Spins of electrons in CMOS quantum dots combine exquisite quantum properties and scalable fabrication. In the age of quantum technology, however, the metrics that crowned Si/SiO2 as the microelectronics standard need to be reassessed with respect to their impact upon qubit performance. We chart the spin qubit variability due to the unavoidable atomic-scale roughness of the Si/SiO$_2$ interface, compiling experiments in 12 devices, and developing theoretical tools to analyse these results. Atomistic tight binding and path integral Monte Carlo methods are adapted for describing fluctuations in devices with millions of atoms by directly analysing their wavefunctions and electron paths instead of their energy spectra. We correlate the effect of roughness with the variability in qubit position, deformation, valley splitting, valley phase, spin-orbit coupling and exchange coupling. These variabilities are found to be bounded and lie within the tolerances for scalable architectures for quantum computing as long as robust control methods are incorporated.

Hermitian Bulk -- Non-Hermitian Boundary Correspondence. (arXiv:2304.03742v2 [cond-mat.mes-hall] UPDATED)
Frank Schindler, Kaiyuan Gu, Biao Lian, Kohei Kawabata

Non-Hermitian band theory distinguishes between line gaps and point gaps. While point gaps can give rise to intrinsic non-Hermitian band topology without Hermitian counterparts, line-gapped systems can always be adiabatically deformed to a Hermitian limit. Here we show that line-gap topology and point-gap topology can be intricately connected: topological line-gapped systems in $d$ dimensions induce nontrivial point-gap topology on their $(d-1)$-dimensional boundaries when suitable internal and spatial symmetries are present. Since line-gapped systems essentially realize Hermitian topological phases, this establishes a correspondence between Hermitian bulk topology and intrinsic non-Hermitian boundary topology. For the correspondence to hold, no non-Hermitian perturbations are required in the bulk itself, so that the bulk can be purely Hermitian. Concomitantly, the presence of non-Hermitian perturbations in the bulk does not affect any results as long as they do not close the bulk line gap. On the other hand, non-Hermitian perturbations are essential on the boundary to open a point gap. The non-Hermitian boundary topology then further leads to higher-order skin modes, as well as chiral and helical hinge modes, that are protected by point gaps and hence unique to non-Hermitian systems. We identify all the internal symmetry classes where bulk line-gap topology induces boundary point-gap topology as long as an additional spatial symmetry is present, and establish the correspondence between their topological invariants. There also exist some symmetry classes where the Hermitian edge states remain stable, in the sense that even a point gap cannot open on the boundary.

Topological edge state transfer via topological adiabatic passage. (arXiv:2305.14529v3 [quant-ph] UPDATED)
Chong Wang, Xiu Gu, Shu Chen, Yu-xi Liu

The study of quantum state transfer has led to a variety of research efforts utilizing quantum simulators. By exploiting the tunability of the qubit frequency and qubit-qubit coupling, a superconducting qubit chain can simulate various topological band models. In our study, we demonstrate that a spin-up state can be transported along a topological qubit chain by modulating the coupling strengths and the qubit frequencies. We show that the Hilbert space of the qubit chain can be restricted to the subspace of two edge states in this process, while the Hamiltonian degenerates into a two-state Landau-Zener (LZ) model. Furthermore, we prove that the state transfer process in this topological qubit chain is equivalent to the topological adiabatic passage of the LZ model. With this analysis, we generalize the state transfer approach from single-qubit Fock states to two-qubit Bell states.

Topological Phases in Magnonics. (arXiv:2305.14861v2 [cond-mat.mes-hall] UPDATED)
Fengjun Zhuo, Jian Kang, Aurélien Manchon, Zhenxiang Cheng

Magnonics or magnon spintronics is an emerging field focusing on generating, detecting, and manipulating magnons. As charge-neutral quasi-particles, magnons are promising information carriers because of their low energy dissipation and long coherence length. In the past decade, topological phases in magnonics have attracted intensive attention due to their fundamental importance in condensed-matter physics and potential applications of spintronic devices. In this review, we mainly focus on recent progress in topological magnonics, such as the Hall effect of magnons, magnon Chern insulators, topological magnon semimetals, etc. In addition, the evidence supporting topological phases in magnonics and candidate materials are also discussed and summarized. The aim of this review is to provide readers with a comprehensive and systematic understanding of the recent developments in topological magnonics.

Extreme Value Statistics and Arcsine Laws of Brownian Motion in the Presence of a Permeable Barrier. (arXiv:2306.03157v2 [cond-mat.stat-mech] UPDATED)
Toby Kay, Luca Giuggioli

The Arcsine laws of Brownian motion are a collection of results describing three different statistical quantities of one-dimensional Brownian motion: the time at which the process reaches its maximum position, the total time the process spends in the positive half-space and the time at which the process crosses the origin for the last time. Remarkably the cumulative probabilities of these three observables all follows the same distribution, the Arcsine distribution. But in real systems, space is often heterogeneous, and these laws are likely to hold no longer. In this paper we explore such a scenario and study how the presence of a spatial heterogeneity alters these Arcsine laws. Specifically we consider the case of a thin permeable barrier, which is often employed to represent diffusion impeding heterogeneities in physical and biological systems such as multilayer electrodes, electrical gap junctions, cell membranes and fragmentation in the landscape for dispersing animals. Using the Feynman-Kac formalism and path decomposition techniques we are able to find the exact time-dependence of the probability distribution of the three statistical quantities of interest. We show that a permeable barrier has a large impact on these distributions at short times, but this impact is less influential as time becomes long. In particular, the presence of a barrier means that the three distributions are no longer identical with symmetry about their means being broken. We also study a closely related statistical quantity, namely, the distribution of the maximum displacement of a Brownian particle and show that it deviates significantly from the usual half-Gaussian form.

Frame potential of Brownian SYK model of Majorana and Dirac fermions. (arXiv:2306.11160v2 [cond-mat.dis-nn] UPDATED)
Anastasiia Tiutiakina, Andrea De Luca, Jacopo De Nardis

We consider the Brownian SYK, i.e. a system of $N$ Majorana (Dirac) fermions with a white-noise $q$-body interaction term. We focus on the dynamics of the Frame potentials, a measure of the scrambling and chaos, given by the moments of the overlap between two independent realisations of the model. By means of a Keldysh path-integral formalism, we compute its early and late-time value. We show that, for $q>2$, the late time path integral saddle point correctly reproduces the saturation to the value of the Haar frame potential. On the contrary, for $q=2$, the model is quadratic and consistently we observe saturation to the Haar value in the restricted space of Gaussian states (Gaussian Haar). The latter is characterised by larger system size corrections that we correctly capture by counting the Goldstone modes of the Keldysh saddle point.

Lecture Notes on Generalized Symmetries and Applications. (arXiv:2307.09215v2 [hep-th] UPDATED)
Ran Luo, Qing-Rui Wang, Yi-Nan Wang

In this lecture note, we give a basic introduction to the rapidly developing concepts of generalized symmetries, from the perspectives of both high energy physics and condensed matter physics. In particular, we emphasize on the (invertible) higher-form and higher-group symmetries. For the physical applications, we discuss the geometric engineering of QFTs in string theory and the symmetry-protected topological (SPT) phases in condensed matter physics.

The lecture note is based on a short course on generalized symmetries, jointly given by Yi-Nan Wang and Qing-Rui Wang in Feb. 2023, which took place at School of Physics, Peking University (

Competing mechanisms govern the thermal rectification behavior in semi-stochastic polycrystalline graphene with graded grain-density distribution. (arXiv:2307.12940v2 [cond-mat.mtrl-sci] UPDATED)
Simanta Lahkar, Raghavan Ranganathan

Thermal rectifiers are devices that have different thermal conductivities in opposing directions of heat flow. The realization of practical thermal rectifiers relies significantly on a sound understanding of the underlying mechanisms of asymmetric heat transport, and two-dimensional materials offer a promising opportunity in this regard owing to their simplistic structures together with a vast possibility of tunable imperfections. However, the in-plane thermal rectification mechanisms in 2D materials like graphene having directional gradients of grain sizes have remained elusive. In fact, understanding the heat transport mechanisms in polycrystalline graphene, which are more practical to synthesize than large-scale single-crystal graphene, could potentially allow a unique opportunity to combine with other defects and designs for effective optimization of the thermal rectification property. In this work, we investigated the thermal rectification behavior in periodic atomistic models of polycrystalline graphene whose grain arrangements were generated semi-stochastically in order to have different gradient grain-density distributions along the in-plane heat flow direction. We employed the centroid Voronoi tessellation technique to generate realistic grain boundary structures for graphene, and the non-equilibrium molecular dynamics simulations method was used to calculate the thermal conductivities and thermal rectification values. Additionally, detailed phonon characteristics and propagating phonon spatial energy densities were analyzed based on the fluctuation-dissipation theory to elucidate the competitive interplay between two underlying mechanisms that determine the degree of asymmetric heat flow in graded polycrystalline graphene.

Weyl phonons in chiral crystals. (arXiv:2307.13378v2 [cond-mat.mtrl-sci] UPDATED)
Tiantian Zhang, Zhiheng Huang, Zitian Pan, Luojun Du, Guangyu Zhang, Shuichi Murakami

Chirality is an indispensable concept that pervades fundamental science and nature, manifesting itself in diverse forms such as chiral quasiparticles and chiral structures. Of particular interest are Weyl phonons carrying specific Chern numbers and chiral phonons doing circular motions in crystals. Up to now, Weyl and chiral phonons have been studied independently and the interpretations of chirality seem to be different in these two concepts, impeding our understanding. Here, we demonstrate that Weyl and chiral phonons are entangled in chiral crystals. Employing a typical chiral crystal of elementary tellurium (Te) as a case study, we expound on the intrinsic relationship between Chern number of Weyl phonons and pseudo-angular momentum (PAM) of chiral phonons. In light of the mutual coupling, we propose Raman scattering as a new technique to demonstrate the existence of Weyl phonons in Te, by detecting the chirality-induced energy splitting between the two constituent chiral phonon branches for Weyl phonons. By using the same experimental approach, we also observe the obstructed phonon surface states for the first time.

Broadband parametric amplification for multiplexed SiMOS quantum dot signals. (arXiv:2307.14717v2 [cond-mat.mes-hall] UPDATED)
Victor Elhomsy, Luca Planat, David J. Niegemann, Bruna Cardoso-Paz, Ali Badreldin, Bernhard Klemt, Vivien Thiney, Renan Lethiecq, Eric Eyraud, Matthieu C. Dartiailh, Benoit Bertrand, Heimanu Niebojewski, Christopher Bäuerle, Maud Vinet, Tristan Meunier, Nicolas Roch, Matias Urdampilleta

Spins in semiconductor quantum dots hold great promise as building blocks of quantum processors. Trapping them in SiMOS transistor-like devices eases future industrial scale fabrication. Among the potentially scalable readout solutions, gate-based dispersive radiofrequency reflectometry only requires the already existing transistor gates to readout a quantum dot state, relieving the need for additional elements. In this effort towards scalability, traveling-wave superconducting parametric amplifiers significantly enhance the readout signal-to-noise ratio (SNR) by reducing the noise below typical cryogenic low-noise amplifiers, while offering a broad amplification band, essential to multiplex the readout of multiple resonators. In this work, we demonstrate a 3GHz gate-based reflectometry readout of electron charge states trapped in quantum dots formed in SiMOS multi-gate devices, with SNR enhanced thanks to a Josephson traveling-wave parametric amplifier (JTWPA). The broad, tunable 2GHz amplification bandwidth combined with more than 10dB ON/OFF SNR improvement of the JTWPA enables frequency and time division multiplexed readout of interdot transitions, and noise performance near the quantum limit. In addition, owing to a design without superconducting loops and with a metallic ground plane, the JTWPA is flux insensitive and shows stable performances up to a magnetic field of 1.2T at the quantum dot device, compatible with standard SiMOS spin qubit experiments.

Collective advantages in finite-time thermodynamics. (arXiv:2306.16534v2 [quant-ph] CROSS LISTED)
Alberto Rolandi, Martí Perarnau-Llobet

A central task in finite-time thermodynamics is to minimize the excess or dissipated work, $W_{\rm diss}$, when manipulating the state of a system immersed in a thermal bath. We consider this task for an $N$-body system, whose constituents are identical and uncorrelated at the beginning and end of the process. In the regime of slow but finite-time processes, we show that $W_{\rm diss}$ can be dramatically reduced by considering collective protocols in which interactions are suitably created along the protocol. This can even lead to a sub-linear growth of $W_{\rm diss}$ with $N$: $W_{\rm diss}\sim N^x$ with $x<1$; to be contrasted to the expected $W_{\rm diss}\sim N$ satisfied in any non-interacting protocol. We derive the fundamental limits to such collective advantages and show that $x=0$ is in principle possible, which however requires highly non-local $N$-body interactions. We then explore collective processes with realistic many-body interacting models, in particular a 1D spin chain and an all-to-all spin model, achieving noticeable gains under realistic levels of control. As an application of these results, we focus on the erasure of information in finite time, and prove a faster convergence to Landauer's erasure bound.

Found 8 papers in prb
Date of feed: Thu, 03 Aug 2023 03:17:07 GMT

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]+)

Superexchange interaction in insulating ${\mathrm{EuZn}}_{2}{\mathrm{P}}_{2}$
Karan Singh, Shovan Dan, A. Ptok, T. A. Zaleski, O. Pavlosiuk, P. Wiśniewski, and D. Kaczorowski
Author(s): Karan Singh, Shovan Dan, A. Ptok, T. A. Zaleski, O. Pavlosiuk, P. Wiśniewski, and D. Kaczorowski

We report magnetic and transport properties of single-crystalline ${\mathrm{EuZn}}_{2}{\mathrm{P}}_{2}$, which has trigonal ${\mathrm{CaAl}}_{2}{\mathrm{Si}}_{2}$-type crystal structure and orders antiferromagnetically at $≈23\phantom{\rule{4pt}{0ex}}\mathrm{K}$. Easy $ab$-plane magneto-crystalline …

[Phys. Rev. B 108, 054402] Published Wed Aug 02, 2023

Macroscopic dynamics of superfluid $^{3}\mathrm{He}$ with a spatially modulated pair density wave
Harald Pleiner and Helmut R. Brand
Author(s): Harald Pleiner and Helmut R. Brand

We discuss the macroscopic behavior of the superfluid $^{3}\mathrm{He}$ phase (pair density wave phase) with a spatially modulated pair density wave recently observed experimentally. As an order parameter we assume, based on the experimental results and a Landau-type model, a variation of the phase …

[Phys. Rev. B 108, 054502] Published Wed Aug 02, 2023

Random geometry at an infinite-randomness fixed point
Akshat Pandey, Aditya Mahadevan, and Aditya Cowsik
Author(s): Akshat Pandey, Aditya Mahadevan, and Aditya Cowsik

We study the low-energy physics of the critical ($2+1$)-dimensional random transverse-field Ising model. The one-dimensional version of the model is a paradigmatic example of a system governed by an infinite-randomness fixed point, for which many results on the distributions of observables are known…

[Phys. Rev. B 108, 064201] Published Wed Aug 02, 2023

Strange metal phase of disordered magic-angle twisted bilayer graphene at low temperatures: From flat bands to weakly coupled Sachdev-Ye-Kitaev bundles
Chenan Wei (魏晨岸) and Tigran A. Sedrakyan
Author(s): Chenan Wei (魏晨岸) and Tigran A. Sedrakyan

We use stochastic expansion and exact diagonalization to study magic-angle twisted bilayer graphene (TBG) on a disordered substrate. We show that the substrate-induced strong Coulomb disorder in TBG with the chemical potential at the level of the flat bands drives the system to a network of weakly c…

[Phys. Rev. B 108, 064202] Published Wed Aug 02, 2023

Holographic theory for continuous phase transitions: Emergence and symmetry protection of gaplessness
Arkya Chatterjee and Xiao-Gang Wen
Author(s): Arkya Chatterjee and Xiao-Gang Wen

Two global symmetries are holoequivalent if their algebras of local symmetric operators are isomorphic. A holoequivalent class of global symmetries is described by a topological order (TO) in one higher dimension (called symmetry TO), which leads to a symmetry/topological-order (Symm/TO) corresponde…

[Phys. Rev. B 108, 075105] Published Wed Aug 02, 2023

Light controlled topological plasmonics in a graphene lattice arrayed by metal nanoparticles
Lu Zhang, Xi-Ming Wang, Xin-Miao Qiu, Zhigang Wang, and Jie-Yun Yan
Author(s): Lu Zhang, Xi-Ming Wang, Xin-Miao Qiu, Zhigang Wang, and Jie-Yun Yan

The implementation of topology on photonics has opened new functionalities of photonic systems, such as the topologically protected boundary photonic modes. In this study, we investigate topological plasmonics in a graphene lattice arrayed with metal nanoparticles and irradiated by a polarized light…

[Phys. Rev. B 108, 085402] Published Wed Aug 02, 2023

Spin-dependent gain and loss in photonic quantum spin Hall systems
Tian-Rui Liu, Kai Bai, Jia-Zheng Li, Liang Fang, Duanduan Wan, and Meng Xiao
Author(s): Tian-Rui Liu, Kai Bai, Jia-Zheng Li, Liang Fang, Duanduan Wan, and Meng Xiao

Topological phases are greatly enriched by including non-Hermiticity. While most works focus on the topology of the eigenvalues and eigenstates, how topologically nontrivial non-Hermitian systems behave in dynamics has only drawn limited attention. Here, we consider a breathing honeycomb lattice kno…

[Phys. Rev. B 108, L081101] Published Wed Aug 02, 2023

Tuning heat transport in graphene by tension
H. Liu, M. Lee, M. Šiškins, H. S. J. van der Zant, P. G. Steeneken, and G. J. Verbiest
Author(s): H. Liu, M. Lee, M. Šiškins, H. S. J. van der Zant, P. G. Steeneken, and G. J. Verbiest

The speed of sound and flexural phonons in two-dimensional materials depends strongly on the tension in these ultraflexible membranes. Here, the authors experimentally demonstrate that freestanding graphene membranes cool down 33% faster when increasing tension by electrostatic gating. They attribute this effect mainly to improved acoustic impedance match of flexural phonons at the boundaries of the membrane and thus provide a route towards electronic devices and circuits for high-speed control of nanoscale heat transport.

[Phys. Rev. B 108, L081401] Published Wed Aug 02, 2023

Found 1 papers in nano-lett
Date of feed: Wed, 02 Aug 2023 13:13:53 GMT

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]+)

[ASAP] Hierarchically Plied Mechano-Electrochemical Energy Harvesting Using a Scalable Kinematic Sensing Textile Woven from a Graphene-Coated Commercial Cotton Yarn
Juwan Kim, Jun Ho Noh, Sungwoo Chun, Seon Jeong Kim, Hyeon Jun Sim, and Changsoon Choi

TOC Graphic

Nano Letters
DOI: 10.1021/acs.nanolett.3c02221

Found 1 papers in science-adv
Date of feed: Wed, 02 Aug 2023 19:08:54 GMT

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]+)

Determination of the preferred epitaxy for III-nitride semiconductors on wet-transferred graphene
Fang Liu, Tao Wang, Xin Gao, Huaiyuan Yang, Zhihong Zhang, Yucheng Guo, Ye Yuan, Zhen Huang, Jilin Tang, Bowen Sheng, Zhaoying Chen, Kaihui Liu, Bo Shen, Xin-Zheng Li, Hailin Peng, Xinqiang Wang
Science Advances, Volume 9, Issue 31, August 2023.

Found 2 papers in nat-comm

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]+)

Adiabatic topological photonic interfaces
< author missing >

Unraveling surface structures of gallium promoted transition metal catalysts in CO2 hydrogenation
< author missing >