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

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Variational adiabatic transport of tensor networks. (arXiv:2311.00748v1 [quant-ph])
Hyeongjin Kim, Matthew T. Fishman, Dries Sels

We discuss a tensor network method for constructing the adiabatic gauge potential -- the generator of adiabatic transformations -- as a matrix product operator, which allows us to adiabatically transport matrix product states. Adiabatic evolution of tensor networks offers a wide range of applications, of which two are explored in this paper: improving tensor network optimization and scanning phase diagrams. By efficiently transporting eigenstates to quantum criticality and performing intermediary density matrix renormalization group (DMRG) optimizations along the way, we demonstrate that we can compute ground and low-lying excited states faster and more reliably than a standard DMRG method at or near quantum criticality. We demonstrate a simple automated step size adjustment and detection of the critical point based on the norm of the adiabatic gauge potential. Remarkably, we are able to reliably transport states through the critical point of the models we study.


"Tattered" membrane. (arXiv:2311.00752v1 [cond-mat.stat-mech])
Pierre Le Doussal, Leo Radzihovsky

Ideal crystalline membranes, realized by graphene and other atomic monolayers, exhibit rich physics - a universal anomalous elasticity of the critical "flat" phase characterized by a negative Poisson ratio, universally singular elastic moduli, order-from-disorder and a crumpling transition. We formulate a generalized $D$-dimensional field theory, parameterized by an $O(d)\times O(D)$ tensor field with an {\it energetic} longitudinal constraint. For a soft constraint the resulting field theory describes a new class of a fluctuating "tattered" membranes, exhibiting a nonzero density of topological connectivity defects - slits, cracks and faults at an effective medium level. For hard, infinite-coupling constraint, the model reproduces the conventional crystalline membrane and its crumpling transition, and thereby demonstrates the essence of the difference between an elastic membrane and conventional field theories. Two additional fixed points emerge within the critical manifold, (i) globally attractive, "isotropic" $O(d)\times O(D)$, and (ii) "transverse", which in $D=2$ is the exact "dual" of the elastic membrane. Their properties are obtained in general $D,d$ from the renormalization group and the self-consistent screening analyses.


Floquet engineering in the presence of optically excited carriers. (arXiv:2311.00916v1 [cond-mat.mes-hall])
Mitchell A. Conway, Jonathan O. Tollerud, Thi-Hai-Yen Vu, Kenji Watanabe, Takashi Taniguchi, Michael S. Fuhrer, Mark T. Edmonds, Jeffrey A. Davis

Floquet engineering provides an optical means to manipulate electronic bandstructures, however, carriers excited by the pump field can lead to an effective heating, and can obscure measurement of the band changes. A recent demonstration of the effects of Floquet engineering on a coherent ensemble of excitons in monolayer WS$_2$ proved particularly sensitive to non-adiabatic effects, while still being able to accurately resolve bandstructure changes. Here, we drive an AC-Stark effect in monolayer WS$_2$ using pulses with constant fluence but varying pulse duration (from 25-235~fs). With shorter pump pulses, the corresponding increase in peak intensity introduces additional carriers via two-photon absorption, leading to additional decoherence and peak broadening (which makes it difficult to resolve the AC-Stark shift). We use multidimensional coherent spectroscopy to create a coherent ensemble of excitons in monolayer WS$_2$ and measure the evolution of the coherence throughout the duration of the Floquet pump pulse. Changes to the amplitude of the macroscopic coherence quantifies the additional broadening. At the same time, the evolution of the average phase allows the instantaneous changes to the bandstructure to be quantified, and is not impacted by the additional broadening. This approach to measuring the evolution of Floquet-Bloch states demonstrates a means to quantify effective heating and non-adiabaticity caused by excited carriers, while at the same time resolving the coherent evolution of the bandstructure.


Topological edge spectrum along curved interfaces. (arXiv:2311.00918v1 [math-ph])
Alexis Drouot, Xiaowen Zhu

We prove that that if the boundary of a topological insulator divides the plane in two regions containing arbitrarily large balls, then it acts as a conductor. Conversely, we show that topological insulators that fit within strips do not need to admit conducting boundary modes.


Effect of Confinement and Topology: 2-TIPS vs MIPS. (arXiv:2311.00929v1 [cond-mat.soft])
Nayana Venkatareddy, Jaydeep Mandal, Prabal K. Maiti

2-TIPS (Two Temperature induced phase separation) refers to the phase separation phenomenon observed in mixtures of active and passive particles which are modelled using scalar activity. The active particles are connected to a thermostat at high temperature while the passive particles are connected to the thermostat at low temperature and the relative temperature difference between "hot" and "cold" particles is taken as the measure of the activity of the non-equilibrium system. The study of such binary mixtures of hot and cold particles under various kinds of confinement is an important problem in many physical and biological processes. The nature and extent of phase separation are heavily influenced by the geometry of confinement, activity, and density of the non-equilibrium binary mixture. Investigating such 3D binary mixtures confined by parallel walls, we observe that, the active and passive particles phase separate, but the extent of phase separation is reduced compared to bulk phase separation at high densities and enhanced at low densities. However, when the binary mixture of active and passive particles is confined inside a spherical cavity, the phase separation is radial for small radii of the confining sphere and the extent of phase separation is higher compared to their bulk counterparts. Confinement leads to interesting properties in the passive(cold) region like enhanced layering and high compression in the direction parallel to the confining wall. In 2D, both the bulk and confined systems of the binary mixture show a significant decrement in the extent of phase separation at higher densities. This observation is attributed to the trapping of active particles inside the passive cluster, which increases with density. similar phase co-existence.


The generation and detection of the spin-valley-polarization in semi-Dirac materials. (arXiv:2311.00948v1 [cond-mat.supr-con])
Yupeng Huang (1), R. Shen (1 and 2) ((1) National Laboratory of Solid State Microstructures and School of Physics, Nanjing University, Nanjing, 210093, China, (2) Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, China)

We investigated the transport properties in a normal metal/ferromagnet/normal metal/superconductor junction based on semi-Dirac materials with inverted energy gap. With a scattering matrix approach, we show that the electron transport in the junction is spin-valley-polarized due to the ferromagnetic exchange energy. It is also shown that the Andreev reflection is strongly suppressed, which is a clear experimental signal for the spin-valley-polarization in semi-Dirac materials.


Superconducting Properties of Topological Semimetal 1$T$-RhSeTe. (arXiv:2311.01019v1 [cond-mat.supr-con])
C. Patra, T. Agarwal, Arushi, P. Manna, N. Bhatt, R. S. Singh, R. P. Singh

Platinum-group transition-metal dichalcogenides have emerged as a subject of considerable interest in condensed matter physics due to their remarkable topological properties and unconventional superconducting behavior. In this study, we report the synthesis and superconducting characteristics of a new Dirac-type topological semimetallic compound 1$T$-RhSeTe. It shows type-II superconductivity with a superconducting transition temperature of 4.72 K and a high upper critical field. The coexistence of superconductivity and topological properties makes it a prime candidate for hosting topological superconductivity.


Probing interlayer interactions and commensurate-incommensurate transition in twisted bilayer graphene through Raman spectroscopy. (arXiv:2311.01029v1 [cond-mat.mtrl-sci])
Vineet Pandey, Subhendu Mishra, Nikhilesh Maity, Sourav Paul, Abhijith M B, Ajit Roy, Nicholas R Glavin, Kenji Watanabe, Takashi Taniguchi, Abhishek Kumar Singh, Vidya Kochat

Twisted 2D layered materials have garnered a lot of attention recently as a class of 2D materials whose interlayer interactions and electronic properties are dictated by the relative rotation / twist angle between the adjacent layers. In this work, we explore a prototype of such a twisted 2D system, artificially stacked twisted bilayer graphene (TBLG), where we probe the changes in the interlayer interactions and electron-phonon scattering pathways as the twist angle is varied from 0{\deg} to 30{\deg}, using Raman spectroscopy. The long range Moir\'e potential of the superlattice gives rise to additional intravalley and intervalley scattering of the electrons in TBLG which have been investigated through their Raman signatures. The density functional theory (DFT) calculations of the electronic band structure of the TBLG superlattices was found to be in agreement with the resonant Raman excitations across the van Hove singularities in the valence and conduction bands predicted for TBLG due to hybridization of bands from the two layers. We also observe that the relative rotation between the graphene layers has a marked influence on the second order overtone and combination Raman modes signalling a commensurate-incommensurate transition in TBLG as the twist angle increases. This serves as a convenient and rapid characterization tool to determine the degree of commensurability in TBLG systems.


Magnesium hydride films deposited on flexible substrates: Structure, morphology and hydrogen sorption properties. (arXiv:2311.01071v1 [physics.app-ph])
Huy Le-Quoc (NEEL - MRS, LPSC), Marie Coste (NEEL - MRS, LPSC), Ana Lacoste (LPSC), L. Laversenne (NEEL - MRS)

1.8 micrometer-thick magnesium hydride films were synthesized in a single-step process by reactive plasma-assisted sputtering. The MgH2 thin films, which were deposited on two types of flexible surfaces (namely graphite and polyimide foils) were found to adhere on both substrates. In all cases, XRD analysis revealed an as-deposited thin film consisting of alpha-MgH2, a tetragonal, rutile-type crystal structure (space group \#136). The hydrogen sorption capacities of the uncapped films were studied over successive desorption/absorption cycles performed at 350 {\textdegree}C. The first desorption always shows a slow kinetics that can be explained by a superficial oxidation of the films. However, once the passivating layer is removed, the following dehydrogenations occur faster. Multiple cycling of the film deposited on polyimide resulted in delamination of the film and its conversion into loose powder. As for MgH2 deposited on the flexible graphite substrate, a fully reversible capacity was observed over 28 cycles with no delamination of the film. Upon cycling, the microstructure of the film has evolved from homogeneous fibrous to an untextured morphology with a higher degree of crystallinity.


Gapped boundaries of fermionic topological orders and higher central charges. (arXiv:2311.01096v1 [cond-mat.str-el])
Minyoung You

We develop a test for the vanishing of higher central charges of a fermionic topological order, which is a necessary condition for the existence of a gapped boundary, purely in terms of the modular data of the super-modular tensor category. More precisely, we test whether a given super-MTC has $c = 0$ mod $\frac{1}{2}$, and, if so, whether the modular extension with $c =0$ mod $8$ has vanishing higher central charges. The test itself does not require an explicit computation of the modular extensions and is easily carried out. We apply this test to known examples of super-modular tensor categories. Since our test allows us to obtain information about the chiral central charge of a super-modular tensor category in terms of its modular data without direct knowledge of its modular extensions, this can also be thought of as the first step towards a fermionic analogue of the Gauss-Milgram formula.


An Optimal Medium for Haptics. (arXiv:2311.01179v1 [cond-mat.mtrl-sci])
Thomas Daunizeau, Sinan Haliyo, Vincent Hayward

Humans rely on multimodal perception to form representations of the world. This implies that environmental stimuli must remain consistent and predictable throughout their journey to our sensory organs. When it comes to vision, electromagnetic waves are minimally affected when passing through air or glass treated for chromatic aberrations. Similar conclusions can be drawn for hearing and acoustic waves. However, tools that propagate elastic waves to our cutaneous afferents tend to color tactual perception due to parasitic mechanical attributes such as resonances and inertia. These issues are often overlooked, despite their critical importance for haptic devices that aim to faithfully render or record tactile interactions. Here, we investigate how to optimize this mechanical transmission with sandwich structures made from rigid, lightweight carbon fiber sheets arranged around a 3D-printed lattice core. Through a comprehensive parametric evaluation, we demonstrate that this design paradigm provides superior haptic transparency. Drawing an analogy with topology optimization, our solution approaches a foreseeable technological limit. This novel medium offers a practical way to create high-fidelity haptic interfaces, opening new avenues for research on tool-mediated interactions.


Scaling Law for Time-Reversal-Odd Nonlinear Transport. (arXiv:2311.01219v1 [cond-mat.mes-hall])
Yue-Xin Huang, Cong Xiao, Shengyuan A. Yang, Xiao Li

Time-reversal-odd ($\mathcal{T}$-odd) nonlinear current response has been theoretically proposed and experimentally confirmed recently. However, the role of disorder scattering in the response, especially whether it contributes to the $\sigma_{xx}$-independent term, has not been clarified. In this work, we derive a general scaling law for this effect, which accounts for multiple scattering sources. We show that the nonlinear conductivity is generally a quartic function in $\sigma_{xx}$. Besides intrinsic contribution, extrinsic contributions from scattering also enter the zeroth order term, and their values can be comparable to or even larger than the intrinsic one. Terms beyond zeroth order are all extrinsic. Cubic and quartic terms must involve skew scattering and they signal competition between at least two scattering sources. The behavior of zeroth order extrinsic terms is explicitly demonstrated in a Dirac model. Our finding reveals the significant role of disorder scattering in $\mathcal{T}$-odd nonlinear transport, and establishes a foundation for analyzing experimental result.


Non-Fermi liquid behavior in a correlated flatband pyrochlore lattice. (arXiv:2311.01269v1 [cond-mat.str-el])
Jianwei Huang, Lei Chen, Yuefei Huang, Chandan Setty, Bin Gao, Yue Shi, Zhaoyu Liu, Yichen Zhang, Turgut Yilmaz, Elio Vescovo, Makoto Hashimoto, Donghui Lu, Boris I. Yakobson, Pengcheng Dai, Jiun-Haw Chu, Qimiao Si, Ming Yi

Electronic correlation effects are manifested in quantum materials when either the onsite Coulomb repulsion is large or the electron kinetic energy is small. The former is the dominant effect in the cuprate superconductors or heavy fermion systems while the latter in twisted bilayer graphene or geometrically frustrated metals. However, the simultaneous cooperation of both effects in the same quantum material--the design principle to produce a correlated topological flat bands pinned at the Fermi level--remains rare. Here, using angle-resolved photoemission spectroscopy, we report the observation of a flat band at the Fermi level in a 3$d$ pyrochlore metal CuV$_2$S$_4$. From a combination of first-principles calculations and slave-spin calculations, we understand the origin of this band to be a destructive quantum-interference effect associated with the V pyrochlore sublattice and further renormalization to the Fermi level by electron interactions in the partially filled V $t_{2g}$ orbitals. As a result, we find transport behavior that indicates a deviation from Fermi-liquid behavior as well as a large Sommerfeld coefficient. Our work demonstrates the pathway into correlated topology by constructing and pinning correlated flat bands near the Fermi level out of a pure $d$-electron system by the combined cooperation of local Coulomb interactions and geometric frustration in a pyrochlore lattice system.


Unravelling the atomic and electronic structure of nanocrystals on superconducting Nb(110): Impact of the oxygen monolayer. (arXiv:2311.01275v1 [cond-mat.mtrl-sci])
Samuel Berman, Ainur Zhussupbekova, Brian Walls, Killian Walshe, Sergei I. Bozhko, Andrei Ionov, David D. O'Regan, Igor V. Shvets, Kuanysh Zhussupbekov

The Niobium surface is almost always covered by a native oxide layer which greatly influences the performance of superconducting devices. Here we investigate the highly stable Niobium oxide overlayer of Nb(110), which is characterised by its distinctive nanocrystal structure as observed by scanning tunnelling microscopy (STM). Our ab-initio density functional theory (DFT) calculations show that a subtle reconstruction in the surface Niobium atoms gives rise to rows of 4-fold coordinated oxygen separated by regions of 3-fold coordinated oxygen. The 4-fold oxygen rows are determined to be the source of the nanocrystal pattern observed in STM, and the two chemical states of oxygen observed in core-level X-ray photoelectron spectroscopy (XPS) are ascribed to the 3-fold and 4-fold oxygens. Furthermore, we find excellent agreement between the DFT calculated electronic structure with scanning tunnelling spectroscopy and valence XPS measurements.


Electrical engineering of topological magnetism in two-dimensional heterobilayers. (arXiv:2311.01294v1 [cond-mat.mtrl-sci])
Nihad Abuawwad, Manuel dos Santos Dias, Hazem Abusara, Samir Lounis

The emergence of topological magnetism in two-dimensional (2D) van der Waals (vdW) magnetic materials promoted 2D heterostructures as key building-blocks of devices for information technology based on topological concepts. Here, we demonstrate the all-electric switching of the topological nature of individual magnetic objects emerging in 2D vdW heterobillayers. We show from the first principles that an external electric field modifies the vdW gap between CrTe $_2$ and (Rh, Ti)Te$_2$ layers and alters the underlying magnetic interactions. This enables switching between ferromagnetic skyrmions and meron pairs in the CrTe$_2$/RhTe$_2$ heterobilayer while it enhances the stability of frustrated antiferromagnetic merons in the CrTe$_2$/TiTe$_2$ heterobilayer. We envision that the electrical engineering of distinct topological magnetic solitons in a single device could pave the way for novel energy-efficient mechanisms to store and transmit information with applications in spintronics.


Method of Mechanical Exfoliation of Bismuth with Micro-Trench Structures. (arXiv:2311.01321v1 [cond-mat.mes-hall])
Oulin Yu, Raphaela Allgayer, Simon Godin, Jacob Lalande, Paolo Fossati, Chunwei Hsu, Thomas Szkopek, Guillaume Gervais

The discovery of graphene led to a burst in search for 2D materials originating from layered atomic crystals coupled by van der Waals force. While bulk bismuth crystals share this layered crystal structure, unlike other group V members of the periodic table, its interlayer bonds are stronger such that traditional mechanical cleavage and exfoliation techniques have shown to be inefficient. In this work, we present a novel mechanical cleavage method for exfoliating bismuth by utilizing the stress concentration effect induced by micro-trench SiO2 structures. As a result, the exfoliated bismuth flakes can achieve thicknesses down to the sub-10 nm range which are analyzed by AFM and Raman spectroscopy.


The Universal Statistical Structure and Scaling Laws of Chaos and Turbulence. (arXiv:2311.01358v1 [cond-mat.stat-mech])
Noam Levi, Yaron Oz

Turbulence is a complex spatial and temporal structure created by the strong non-linear dynamics of fluid flows at high Reynolds numbers. Despite being an ubiquitous phenomenon that has been studied for centuries, a full understanding of turbulence remained a formidable challenge. Here, we introduce tools from the fields of quantum chaos and Random Matrix Theory (RMT) and present a detailed analysis of image datasets generated from turbulence simulations of incompressible and compressible fluid flows. Focusing on two observables: the data Gram matrix and the single image distribution, we study both the local and global eigenvalue statistics and compare them to classical chaos, uncorrelated noise and natural images. We show that from the RMT perspective, the turbulence Gram matrices lie in the same universality class as quantum chaotic rather than integrable systems, and the data exhibits power-law scalings in the bulk of its eigenvalues which are vastly different from uncorrelated classical chaos, random data, natural images. Interestingly, we find that the single sample distribution only appears as fully RMT chaotic, but deviates from chaos at larger correlation lengths, as well as exhibiting different scaling properties.


Topological Waveguide Quantum Sensors. (arXiv:2311.01370v1 [quant-ph])
Tao Zhang, Jiazhong Hu, Xingze Qiu

We present an efficient and robust protocol for quantum-enhanced sensing using a single-spin qubit in the topological waveguide system. Our method relies on the topological-paired bound states, which are localized near the spin and can be effectively regarded as a two-level system. Through the lens of Bayesian inference theory, we show the sensitivity can reach the Heisenberg limit across a large field range. Inheriting from the topological robustness of the waveguide, our sensing protocol is robust against local perturbations. The advantages of our protocol are multifold as it allows for sensing various parameters and uses a product initial state, which can be easily prepared in experiments. We expect this approach would pave the way towards robust topological quantum sensors based on near term quantum platforms such as topological photonics and Rydberg arrays.


Absence of barren plateaus in finite local-depth circuits with long-range entanglement. (arXiv:2311.01393v1 [quant-ph])
Hao-Kai Zhang, Shuo Liu, Shi-Xin Zhang

Ground state preparation is classically intractable for general Hamiltonians. On quantum devices, shallow parameterized circuits can be effectively trained to obtain short-range entangled states under the paradigm of variational quantum eigensolver, while deep circuits are generally untrainable due to the barren plateau phenomenon. In this Letter, we give a general lower bound on the variance of circuit gradients for arbitrary quantum circuits composed of local 2-designs. Based on our unified framework, we prove the absence of barren plateaus in training finite local-depth circuits for the ground states of local Hamiltonians. These circuits are allowed to be deep in the conventional definition of circuit depth so that they can generate long-range entanglement, but their local depths are finite, i.e., there is only a finite number of non-commuting gates acting on individual qubits. This fact suggests that long-range entangled ground states, such as topologically ordered states, are in general possible to be prepared efficiently on quantum devices via variational methods. We validate our analytical results with extensive numerical simulations and demonstrate the effectiveness of variational training using the generalized toric code model.


Low-depth unitary quantum circuits for dualities in one-dimensional quantum lattice models. (arXiv:2311.01439v1 [quant-ph])
Laurens Lootens, Clement Delcamp, Dominic Williamson, Frank Verstraete

A systematic approach to dualities in symmetric (1+1)d quantum lattice models has recently been proposed in terms of module categories over the symmetry fusion categories. By characterizing the non-trivial way in which dualities intertwine closed boundary conditions and charge sectors, these can be implemented by unitary matrix product operators. In this manuscript, we explain how to turn such duality operators into unitary linear depth quantum circuits via the introduction of ancillary degrees of freedom that keep track of the various sectors. The linear depth is consistent with the fact that these dualities change the phase of the states on which they act. When supplemented with measurements, we show that dualities with respect to symmetries encoded into nilpotent fusion categories can be realised in constant depth. The resulting circuits can for instance be used to efficiently prepare short- and long-range entangled states or map between different gapped boundaries of (2+1)d topological models.


Can deep sub-wavelength cavities induce Amperean superconductivity in a 2D material?. (arXiv:2210.10371v2 [cond-mat.supr-con] UPDATED)
Gian Marcello Andolina, Antonella De Pasquale, Francesco Maria Dimitri Pellegrino, Iacopo Torre, Frank H. L. Koppens, Marco Polini

Amperean superconductivity is an exotic phenomenon stemming from attractive effective electron-electron interactions (EEEIs) mediated by a transverse gauge field. Originally introduced in the context of quantum spin liquids and high-Tc superconductors, Amperean superconductivity has been recently proposed to occur at temperatures on the order of 1-20 K in two-dimensional, parabolic-band, electron gases embedded inside deep sub-wavelength optical cavities. In this work, we first generalize the microscopic theory of cavity-induced Amperean superconductivity to the case of graphene and then argue that this superconducting state cannot be achieved in the deep sub-wavelength regime. In the latter regime, indeed, a cavity induces only EEEIs between density fluctuations rather than the current-current interactions which are responsible for Amperean pairing.


Dynamic melting and condensation of topological dislocation modes. (arXiv:2210.15661v2 [cond-mat.mes-hall] UPDATED)
Sanjib Kumar Das, Bitan Roy

Bulk dislocation lattice defects are instrumental in identifying translationally active topological insulators (TATIs), featuring band inversion at a finite momentum (${\bf K}_{\rm inv}$). As such, TATIs host robust gapless modes around the dislocation core, when the associated Burgers vector ${\bf b}$ satisfies ${\bf K}_{\rm inv} \cdot {\bf b}=\pi$ (modulo $2 \pi$). From the time evolution of appropriate density matrices, we show that when a TATI via a real time ramp enters into a trivial or translationally inert topological insulating phase, devoid of gapless dislocation modes, the signatures of the preramp defect modes survive for a long time. More intriguingly, as the system ramps into a TATI phase from any translationally inert insulator, signature of the dislocation mode dynamically builds up near its core, which is prominent for slow ramps. We exemplify these generic outcomes for two-dimensional time-reversal symmetry breaking insulators. Proposed dynamic responses at the dislocation core can be experimentally observed in quantum crystals, optical lattices and metamaterials with time a tunable band gap.


Transport in strained graphene: Interplay of Abelian and axial magnetic fields. (arXiv:2212.00788v2 [cond-mat.mes-hall] UPDATED)
Aqeel Ahmed, Sanjib Kumar Das, Bitan Roy

Immersed in external magnetic fields ($B$), buckled graphene constitutes an ideal tabletop setup, manifesting a confluence of time-reversal symmetry (${\mathcal T}$) breaking Abelian ($B$) and ${\mathcal T}$-preserving strain-induced internal axial ($b$) magnetic fields. In such a system, here we numerically compute two-terminal conductance ($G$), and four- as well as six-terminal Hall conductivity ($\sigma_{xy}$) for spinless fermions. On a flat graphene ($b=0$), the $B$ field produces quantized plateaus at $G=\pm |\sigma_{xy}|=(2n+1) e^2/h$, where $n=0,1,2, \cdots$. The strain induced $b$ field lifts the two-fold valley degeneracy of higher Landau levels and leads to the formation of additional even-integer plateaus at $G=\pm |\sigma_{xy}|= (2,4,\cdots)e^2/h$, when $B>b$. While the same sequence of plateaus is observed for $G$ when $b>B$, the numerical computation of $\sigma_{xy}$ in Hall bar geometries in this regime becomes unstable. A plateau at $G=\sigma_{xy}=0$ always appears with the onset of a charge-density-wave order, causing a staggered pattern of fermionic density between two sublattices of the honeycomb lattice.


Dirac Solitons and Topological Edge States in the $\beta$-Fermi-Pasta-Ulam-Tsingou dimer lattice. (arXiv:2212.02134v2 [nlin.PS] UPDATED)
Rajesh Chaunsali, Panayotis G. Kevrekidis, Dimitri Frantzeskakis, Georgios Theocharis

We consider a dimer lattice of the Fermi-Pasta-Ulam-Tsingou (FPUT) type, where alternating linear couplings have a controllably small difference, and the cubic nonlinearity ($\beta$-FPUT) is the same for all interaction pairs. We use a weakly nonlinear formal reduction within the lattice bandgap to obtain a continuum, nonlinear Dirac-type system. We derive the Dirac soliton profiles and the model's conservation laws analytically. We then examine the cases of the semi-infinite and the finite domains and illustrate how the soliton solutions of the bulk problem can be ``glued'' to the boundaries for different types of boundary conditions. We thus explain the existence of various kinds of nonlinear edge states in the system, of which only one leads to the standard topological edge states observed in the linear limit. We finally examine the stability of bulk and edge states and verify them through direct numerical simulations, in which we observe a solitary wave setting into motion due to the instability.


Formation of a simple cubic antiferromagnet through charge ordering in a double Dirac material. (arXiv:2303.02218v2 [cond-mat.str-el] UPDATED)
T. Berry (1, 2), V. C. Morano (2), T. Halloran (2), X. Zhang (3), T. J. Slade (4, 5), A. Sapkota (4, 5), S. L. Budko (4, 5), W. Xie (6), D. H. Ryan (7), Z. Xu (8), Y. Zhao (8, 9), J. W. Lynn (8), T. Fennell (10), P. C. Canfield (4, 5), C. L. Broholm (2, 11), T. M. McQueen (1, 2, 11) ((1) Department of Chemistry, The Johns Hopkins University, (2) Institute for Quantum Matter and William H. Miller III Department of Physics and Astronomy, The Johns Hopkins University, (3) Department of Chemical and Biomolecular Engineering, The Johns Hopkins University, (4) Ames Laboratory, U.S. Department of Energy, Iowa State University, (5) Department of Physics and Astronomy, Iowa State University, (6) Department of Chemistry and Chemical Biology, Rutgers University, (7) Physics Department and Centre for the Physics of Materials, McGill University, (8) NIST Center for Neutron Research, National Institute of Standards and Technology, (9) Department of Materials Science and Engineering, University of Maryland, (10) Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institut, (11) Department of Materials Science and Engineering, The Johns Hopkins University)

The appearance of spontaneous charge order in chemical systems is often associated with the emergence of novel, and useful, properties. Here we show through single crystal diffraction that the Eu ions in the mixed valent metal EuPd$_3$S$_4$ undergo long-range charge ordering at $T_{\mathrm{CO}} = 340 \mathrm{~K}$ resulting in simple cubic lattices of Eu$^{2+}$ ($J = 7/2$) and Eu$^{3+}$ ($J = 0$) ions. As only one of the two sublattices has a non-magnetic ground state, the charge order results in the emergence of remarkably simple G-type antiferromagnetic order at $T_{\mathrm{N}} = 2.85(6) \mathrm{~K}$, observed in magnetization, specific heat, and neutron diffraction. Application of a $0.3 \mathrm{~T}$ field is sufficient to induce a spin flop transition to a magnetically polarized, but still charge ordered, state. Density functional theory calculations show that this charge order also modifies the electronic degeneracies present in the material: without charge order, EuPd$_3$S$_4$ is an example of a double Dirac material containing 8-fold degenerate electronic states, greater than the maximum degeneracy of six possible in molecular systems. The symmetry reduction from charge order transmutes 8-fold double Dirac states into 4-fold Dirac states, a degeneracy that can be preserved even in the presence of the magnetic order. Our results show not only how charge order can be used to produce interesting magnetic lattices, but also how it can be used to engineer controlled degeneracies in electronic states.


Quantum coherent control of non-linear thermoelectric transport in a triple-dot Aharonov-Bohm heat engine. (arXiv:2303.09202v2 [cond-mat.mes-hall] UPDATED)
Jayasmita Behera, Salil Bedkihal, Bijay Kumar Agarwalla, Malay Bandyopadhyay

We investigate the role of quantum coherence and higher harmonics resulting from multiple-path interference in nonlinear thermoelectricity in a two-terminal triangular triple-dot Aharonov-Bohm (AB) interferometer. We quantify the trade-off between efficiency and power in the nonlinear regime of our simple setup comprising three non-interacting quantum dots (two connected to two biased metallic reservoirs) placed at the vertex of an equilateral triangle, and a magnetic flux $\Phi$ pierces it perpendicularly. For a spatially symmetric setup, we achieve optimal efficiency and power output when the inter-dot tunneling strength is comparable to the dot-lead coupling, AB phase $\phi=\pi/2$. Our analysis reveals that the presence of higher harmonics is necessary but not sufficient to achieve optimal power output. The maximal constructive interference represented by three close-packed resonance peaks of the unit transmission can enhance the power output ($P_{max}\sim 2.35\,\mathrm{fW}$) almost 3.5 times as compared to the case where only a single channel participates in the transport, and the corresponding efficiency is about $0.80\eta_{c}$ where $\eta_{c}$ is the Carnot efficiency. Geometric asymmetries and their effects on efficiency and power output are also investigated. An asymmetric setup characterized by the ratio of the coupling to the source and the drain terminals ($x$) can further enhance the maximum power output $P_{max}\sim 3.85\,\mathrm{fW}$ for $x=1.5$ with the same efficiency as that of the symmetric case. Our investigation reveals that the output power and efficiency are optimal in the wide-band limit. The power output is significantly reduced for the narrow-band case. On the other hand, disorder effects radically reduce the performance of the heat engine.


Coherent Charge Oscillations in a Bilayer Graphene Double Quantum Dot. (arXiv:2303.10119v3 [cond-mat.mes-hall] UPDATED)
Katrin Hecker, Luca Banszerus, Aaron Schäpers, Samuel Möller, Anton Peters, Eike Icking, Kenji Watanabe, Takashi Taniguchi, Christian Volk, Christoph Stampfer

The coherent dynamics of a quantum mechanical two-level system passing through an anti-crossing of two energy levels can give rise to Landau-Zener-St\"uckelberg-Majorana (LZSM) interference. LZSM interference spectroscopy has proven to be a fruitful tool to investigate charge noise and charge decoherence in semiconductor quantum dots (QDs). Recently, bilayer graphene has developed as a promising platform to host highly tunable QDs potentially useful for hosting spin and valley qubits. So far, in this system no coherent oscillations have been observed and little is known about charge noise in this material. Here, we report coherent charge oscillations and $T_2^*$ charge decoherence times in a bilayer graphene double QD. The charge decoherence times are measured independently using LZSM interference and photon assisted tunneling. Both techniques yield $T_2^*$ average values in the range of 400 to 500 ps. The observation of charge coherence allows to study the origin and spectral distribution of charge noise in future experiments.


Replica Symmetry Broken States of some Glass Models. (arXiv:2308.14229v2 [cond-mat.dis-nn] UPDATED)
J. Yeo, M. A. Moore

We have studied in detail the $M$-$p$ balanced spin glass model, especially the case $p=4$. These types of model have relevance to structural glasses. The models possess two kinds of broken replica states; those with one-step replica symmetry breaking (1RSB) and those with full replica symmetry breaking (FRSB). To determine which arises requires studying the Landau expansion to quintic order. There are 9 quintic order coefficients, and 5 quartic order coefficients, whose values we determine for this model. We show that it is only for $2 \leq M < 2.4714 \cdots$ that the transition at mean-field level is to a state with FRSB, while for larger $M$ values there is either a continuous transition to a state with 1RSB (when $ M \leq 3$) or a discontinuous transition for $M > 3$. The Gardner transition from a 1RSB state at low temperatures to a state with FRSB also requires the Landau expansion to be taken to quintic order. Our result for the form of FRSB in the Gardner phase is similar to that found when $2 \leq M < 2.4714\cdots$, but differs from that given in the early paper of Gross et al. [Phys. Rev. Lett. 55, 304 (1985)]. Finally we discuss the effects of fluctuations on our mean-field solutions using the scheme of H\"{o}ller and Read [Phys. Rev. E 101, 042114 (2020)}] and argue that such fluctuations will remove both the continuous 1RSB transition and discontinuous 1RSB transitions when $8 >d \geq 6$ leaving just the FRSB continuous transition. We suggest values for $M$ and $p$ which might be used in simulations to confirm whether fluctuation corrections do indeed remove the 1RSB transitions.


Uniqueness of steady states of Gorini-Kossakowski-Sudarshan-Lindblad equations: a simple proof. (arXiv:2309.00335v3 [quant-ph] UPDATED)
Hironobu Yoshida

We present a simple proof of a sufficient condition for the uniqueness of non-equilibrium steady states of Gorini-Kossakowski-Sudarshan-Lindblad equations. We demonstrate the applications of the sufficient condition using examples of the transverse-field Ising model, the XYZ model, and the tight-binding model with dephasing.


Mathematical results on the chiral model of twisted bilayer graphene (with an appendix by Mengxuan Yang and Zhongkai Tao). (arXiv:2310.20642v2 [cond-mat.mes-hall] UPDATED)
Maciej Zworski, Mengxuan Yang, Zhongkai Tao

The study of twisted bilayer graphene (TBG) is a hot topic in condensed matter physics with special focus on {\em magic angles} of twisting at which TBG acquires unusual properties. Mathematically, topologically non-trivial flat bands appear at those special angles. The chiral model of TBG pioneered by Tarnopolsky--Kruchkov--Vishwanath has particularly nice mathematical properties and we survey, and in some cases, clarify, recent rigorous results which exploit them.


Found 7 papers in prb
Date of feed: Fri, 03 Nov 2023 04:16:55 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]+)|(flatband)|(flat.{1}band)|(LK.{1}99)

Topological gap solitons in Rabi Su-Schrieffer-Heeger lattices
Chunyan Li and Yaroslav V. Kartashov
Author(s): Chunyan Li and Yaroslav V. Kartashov

Topological insulators are unique materials possessing forbidden topological gap and behaving similar to usual insulators in their bulk, but at the same time supporting localized in-gap states at their edges that demonstrate exceptional robustness, because they are protected by topology of the syste…


[Phys. Rev. B 108, 184301] Published Thu Nov 02, 2023

Ultrafast dynamics of electrons excited by femtosecond laser pulses: Spin polarization and spin-polarized currents
Oliver Busch, Franziska Ziolkowski, Ingrid Mertig, and Jürgen Henk
Author(s): Oliver Busch, Franziska Ziolkowski, Ingrid Mertig, and Jürgen Henk

Laser radiation incident on a ferromagnetic sample produces excited electrons and currents whose spin polarization must not be aligned with the magnetization—an effect due to spin-orbit coupling that is ubiquitous in spin- and angle-resolved photoemission. In this paper, we report on a systematic in…


[Phys. Rev. B 108, 184401] Published Thu Nov 02, 2023

Triplet superconductivity and spin density wave in biased AB bilayer graphene
A. O. Sboychakov, A. V. Rozhkov, and A. L. Rakhmanov
Author(s): A. O. Sboychakov, A. V. Rozhkov, and A. L. Rakhmanov

We examine spin density wave and triplet superconductivity as possible ground states of the Bernal bilayer graphene. The spin density wave is stable for the unbiased and undoped bilayer. Both the doping and the applied bias voltage destroy this phase. We show that, when biased and slightly doped, a …


[Phys. Rev. B 108, 184503] Published Thu Nov 02, 2023

Multiple superconducting phases driven by pressure in the topological insulator ${\mathrm{GeSb}}_{4}{\mathrm{Te}}_{7}$
W. Zhou, B. Li, Y. Shen, J. J. Feng, C. Q. Xu, H. T. Guo, Z. He, B. Qian, Ziming Zhu, and Xiaofeng Xu
Author(s): W. Zhou, B. Li, Y. Shen, J. J. Feng, C. Q. Xu, H. T. Guo, Z. He, B. Qian, Ziming Zhu, and Xiaofeng Xu

Tuning superconductivity in topological materials by means of chemical substitution, electrostatic gating, or pressure is thought to be an effective route towards realizing topological superconductivity with their inherent Majorana fermions, the manipulation of which may form the basis for future to…


[Phys. Rev. B 108, 184504] Published Thu Nov 02, 2023

Magnetic bound states of iron clusters on a superconductor
Silas Amann, Nóra Kucska, András Lászlóffy, Nicolas Néel, Balázs Újfalussy, Levente Rózsa, Krisztián Palotás, and Jörg Kröger
Author(s): Silas Amann, Nóra Kucska, András Lászlóffy, Nicolas Néel, Balázs Újfalussy, Levente Rózsa, Krisztián Palotás, and Jörg Kröger

The magnetic exchange interaction of ${\mathrm{Fe}}_{n}$ $(n=1,2,3)$ clusters with the quasiparticles of superconducting Pb(111) is probed by scanning tunneling spectroscopy of Yu-Shiba-Rusinov states. The spectral weight of the Yu-Shiba-Rusinov resonances is shifted from the coherence peaks in the …


[Phys. Rev. B 108, 195403] Published Thu Nov 02, 2023

Flat band induced local Hilbert space fragmentation
Eulàlia Nicolau, Anselmo M. Marques, Ricardo G. Dias, and Verònica Ahufinger
Author(s): Eulàlia Nicolau, Anselmo M. Marques, Ricardo G. Dias, and Verònica Ahufinger

We demonstrate that a complete class of flat-band lattices with underlying commutative local symmetries exhibit a locally fragmented Hilbert space. The equitable partition theorem ensures distinct parities for the compact localized states (CLSs) present in this class of flat-band lattices and the ex…


[Phys. Rev. B 108, 205104] Published Thu Nov 02, 2023

Controllable single-spin evolution at subharmonics of electric dipole spin resonance enhanced by four-level Landau-Zener-Stückelberg-Majorana interference
D. V. Khomitsky, M. V. Bastrakova, V. O. Munyaev, N. A. Zaprudnov, and S. A. Studenikin
Author(s): D. V. Khomitsky, M. V. Bastrakova, V. O. Munyaev, N. A. Zaprudnov, and S. A. Studenikin

Subharmonics of electric dipole spin resonance (EDSR) mediated by Landau-Zener-Stückelberg-Majorana tunneling transitions are studied numerically and analytically in a Zeeman-split four-level system with strong spin-orbit coupling that can be realized, for example, in a GaAs-based double quantum dot…


[Phys. Rev. B 108, 205404] Published Thu Nov 02, 2023

Found 1 papers in pr_res
Date of feed: Fri, 03 Nov 2023 04:16:59 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]+)|(flatband)|(flat.{1}band)|(LK.{1}99)

Correlation-boosted quantum engine: A proof-of-principle demonstration
Marcela Herrera, John H. Reina, Irene D'Amico, and Roberto M. Serra
Author(s): Marcela Herrera, John H. Reina, Irene D'Amico, and Roberto M. Serra

Employing currently available quantum technology, we design and implement a nonclassically correlated SWAP heat engine that allows to achieve an efficiency above the standard Carnot limit. Such an engine also boosts the amount of extractable work, in a wider parameter window, with respect to engine'…


[Phys. Rev. Research 5, 043104] Published Thu Nov 02, 2023

Found 1 papers in nano-lett
Date of feed: Thu, 02 Nov 2023 13:07:17 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]+)|(flatband)|(flat.{1}band)|(LK.{1}99)

[ASAP] Topological Transitions and Surface Umklapp Scattering in Weakly Modulated Periodic Metasurfaces
Kobi Cohen, Shai Tsesses, Shimon Dolev, Yael Blechman, Guy Ankonina, and Guy Bartal

TOC Graphic

Nano Letters
DOI: 10.1021/acs.nanolett.3c02759

Found 1 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]+)|(flatband)|(flat.{1}band)|(LK.{1}99)

Emergent superconductivity in topological-kagome-magnet/metal heterostructures
< author missing >

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]+)|(flatband)|(flat.{1}band)|(LK.{1}99)

Topological Defects in Floquet Circuits, by Mao Tian Tan, Yifan Wang, Aditi Mitra
< author missing >
Submitted on 2023-11-02, refereeing deadline 2023-11-17.