Twisted bilayer graphene is a rich condensed matter system, which allows one to tune energy scales and electronic correlations. The low-energy physics of the resulting moir{\'e} structure can be mathematically described in terms of a diffeomorphism in a continuum formulation. We stress that twisting is just one example of moir{\'e} diffeomorphisms. Another particularly simple and experimentally relevant transformation is a homogeneous isomorphic strain of one of the layers, which gives rise to a nearly identical moir{\'e} pattern (rotated by\ 90 degrees\ relative to the twisted structure) and potentially flat bands. We further observe that low-energy physics of the strained bilayer graphene takes the form of a theory of fermions tunneling between two curved space-times. Conformal transformation of the metrics results in emergent {\textquotedblleft}moir{\'e} energy scales,{\textquotedblright} which can be tuned to be much lower than those in the native theory. This observation generalizes to an arbitrary space-time dimension with or without an underlying lattice or periodicity and suggests a family of toy models of {\textquotedblleft}moir{\'e} gravity{\textquotedblright} with low emergent energy scales. Motivated by these analogies, we present an explicit toy construction of moir{\'e} gravity, where the effective cosmological constant can be made arbitrarily small. We speculate about possible relevance of this scenario to the fundamental vacuum catastrophe in cosmology.

}, doi = {10.1103/PhysRevResearch.4.L022027}, url = {https://link.aps.org/doi/10.1103/PhysRevResearch.4.L022027}, author = {Parhizkar, Alireza and Galitski, Victor} } @article { WOS:000652838200010, title = {Chiral Anomaly in Interacting Condensed Matter Systems}, journal = {Phys. Rev. Lett.}, volume = {126}, number = {18}, year = {2021}, month = {MAY 7}, publisher = {AMER PHYSICAL SOC}, type = {Article}, abstract = {The chiral anomaly is a fundamental quantum mechanical phenomenon which is of great importance to both particle physics and condensed matter physics alike. In the context of QED, it manifests as the breaking of chiral symmetry in the presence of electromagnetic fields. It is also known that anomalous chiral symmetry breaking can occur through interactions alone, as is the case for interacting one-dimensional systems. In this Letter, we investigate the interplay between these two modes of anomalous chiral symmetry breaking in the context of interacting Weyl semimetals. Using Fujikawa{\textquoteright}s path integral method, we show that the chiral charge continuity equation is modified by the presence of interactions which can be viewed as including the effect of the electric and magnetic fields generated by the interacting quantum matter. This can be understood further using dimensional reduction and a Luttinger liquid description of the lowest Landau level. These effects manifest themselves in the nonlinear response of the system. In particular, we find an interaction-dependent density response due to a change in the magnetic field as well as a contribution to the nonequilibrium and inhomogeneous anomalous Hall response while preserving its equilibrium value.}, issn = {0031-9007}, doi = {10.1103/PhysRevLett.126.185303}, author = {Rylands, Colin and Parhizkar, Alireza and Burkov, Anton A. and Galitski, Victor} } @article {green_how_2021, title = {How to profit from quantum technology without building quantum computers}, journal = {Nat. Rev. Phys.}, volume = {3}, number = {3}, year = {2021}, note = {Place: CAMPUS, 4 CRINAN ST, LONDON, N1 9XW, ENGLAND Publisher: SPRINGERNATURE Type: Editorial Material}, month = {mar}, pages = {150{\textendash}152}, abstract = {There are a number of lower risk opportunities to invest in quantum technologies, other than quantum computers, but to make the most of them both specialist knowledge and market awareness are required.}, doi = {10.1038/s42254-021-00290-w}, author = {Green, Dmitry and Soller, Henning and Oreg, Yuval and Galitski, Victor} } @article { WOS:000735454800008, title = {Loschmidt echo of far-from-equilibrium fermionic superfluids}, journal = {Ann. Phys.}, volume = {435}, number = {2, SI}, year = {2021}, month = {DEC}, publisher = {ACADEMIC PRESS INC ELSEVIER SCIENCE}, type = {Article}, abstract = {Non-analyticities in the logarithm of the Loschmidt echo, known as dynamical quantum phase transitions {[}DQPTs], are a recently introduced attempt to classify the myriad of possible phenomena which can occur in far from equilibrium closed quantum systems. In this work, we analytically investigate the Loschmidt echo in nonequilibrium s-wave and topological p(x) + ip(y) fermionic superfluids. We find that the presence of non-analyticities in the echo is not invariant under global rotations of the superfluid phase. We remedy this deficiency by introducing a more general notion of a grand canonical Loschmidt echo. Overall, our study shows that DQPTs are not a good indicator for the long time dynamics of an interacting system. In particular, there are no DQPTs to tell apart distinct dynamical phases of quenched BCS superconductors. Nevertheless, they can signal a quench induced change in the topology and also keep track of solitons emerging from unstable stationary states of a BCS superconductor. (C) 2021 Elsevier Inc. All rights reserved.}, issn = {0003-4916}, doi = {10.1016/j.aop.2021.168554}, author = {Rylands, Colin and Yuzbashyan, Emil A. and Gurarie, Victor and Zabalo, Aidan and Galitski, Victor} } @article { WOS:000672657300001, title = {Solitons in lattice field theories via tight-binding supersymmetry}, journal = {J. High Energy Phys.}, number = {7}, year = {2021}, month = {JUL 9}, publisher = {SPRINGER}, type = {Article}, abstract = {Reflectionless potentials play an important role in constructing exact solutions to classical dynamical systems (such as the Korteweg-de Vries equation), non-perturbative solutions of various large-N field theories (such as the Gross-Neveu model), and closely related solitonic solutions to the Bogoliubov-de Gennes equations in the theory of superconductivity. These solutions rely on the inverse scattering method, which reduces these seemingly unrelated problems to identifying reflectionless potentials of an auxiliary one-dimensional quantum scattering problem. There are several ways of constructing these potentials, one of which is quantum mechanical supersymmetry (SUSY). In this paper, motivated by recent experimental platforms, we generalize this framework to develop a theory of lattice solitons. We first briefly review the classical inverse scattering method in the continuum limit, focusing on the Korteweg-de Vries (KdV) equation and SU(N) Gross-Neveu model in the large N limit. We then generalize this methodology to lattice versions of interacting field theories. Our analysis hinges on the use of trace identities, which are relations connecting the potential of an equation of motion to the scattering data. For a discrete Schrodinger operator, such trace identities had been known as far back as Toda; however, we derive a new set of identities for the discrete Dirac operator. We then use these identities in a lattice Gross-Neveu and chiral Gross-Neveu (Nambu-Jona-Lasinio) model to show that lattice solitons correspond to reflectionless potentials associated with the discrete scattering problem. These models are of significance as they are equivalent to a mean-field theory of a lattice superconductor. To explicitly construct these solitons, we generalize supersymmetric quantum mechanics to tight-binding models. We show that a matrix transformation exists that maps a tight-binding model to an isospectral one which shares the same structure and scattering properties. The corresponding soliton solutions have both modulated hopping and onsite potential, the former of which has no analogue in the continuum limit. We explicitly compute both topological and non-topological soliton solutions as well as bound state spectra in the aforementioned models.}, keywords = {Lattice Integrable Models, Lattice Quantum Field Theory, Solitons Monopoles and Instantons}, issn = {1029-8479}, doi = {10.1007/JHEP07(2021)055}, author = {Balasubramanian, Shankar and Patoary, Abu and Galitski, Victor} } @article { ISI:000530026700003, title = {Drag viscosity of metals and its connection to Coulomb drag}, journal = {Phys. Rev. B}, volume = {101}, number = {19}, year = {2020}, month = {MAY 4}, pages = {195106}, publisher = {AMER PHYSICAL SOC}, type = {Article}, abstract = {Recent years have seen a surge of interest in studies of hydrodynamic transport in electronic systems. We investigate the electron viscosity of metals and find a component that is closely related to Coulomb drag. By using linear-response theory, viscosity, which is a transport coefficient for momentum, can be extracted from the retarded correlation function of the momentum flux, i.e., the stress tensor. There exists a previously overlooked contribution to the shear viscosity from the interacting part of the stress tensor which accounts for the momentum flow induced by interactions. This contribution, which we dub drag viscosity, is caused by the frictional drag force due to long-range interactions. It is therefore linked to Coulomb drag which also originates from the interaction-induced drag force. Starting from the Kubo formula and using the Keldysh technique, we compute the drag viscosity of two- and three-dimensional metals along with the drag resistivity of double-layer two-dimensional electronic systems. Both the drag resistivity and drag viscosity exhibit a crossover from quadraticin-T behavior at low temperatures to a linear behavior at higher temperatures. Although the drag viscosity appears relatively small compared with the normal Drude component for the clean metals, it may dominate hydrodynamic transport in some systems, which are discussed in the conclusion.}, issn = {2469-9950}, doi = {10.1103/PhysRevB.101.195106}, author = {Liao, Yunxiang and Galitski, Victor} } @article { ISI:000544526900013, title = {Early-Time Exponential Instabilities in Nonchaotic Quantum Systems}, journal = {Phys. Rev. Lett.}, volume = {125}, number = {1}, year = {2020}, month = {JUL 1}, pages = {014101}, publisher = {AMER PHYSICAL SOC}, type = {Article}, abstract = {The majority of classical dynamical systems are chaotic and exhibit the butterfly effect: a minute change in initial conditions has exponentially large effects later on. But this phenomenon is difficult to reconcile with quantum mechanics. One of the main goals in the field of quantum chaos is to establish a correspondence between the dynamics of classical chaotic systems and their quantum counterparts. In isolated systems in the absence of decoherence, there is such a correspondence in dynamics, but it usually persists only over a short time window, after which quantum interference washes out classical chaos. We demonstrate that quantum mechanics can also play the opposite role and generate exponential instabilities in classically nonchaotic systems within this early-time window. Our calculations employ the out-of-time-ordered correlator (OTOC)-a diagnostic that reduces to the Lyapunov exponent in the classical limit but is well defined for general quantum systems. We show that certain classically nonchaotic models, such as polygonal billiards, demonstrate a Lyapunov-like exponential growth of the OTOC at early times with Planck{\textquoteright}s-constant-dependent rates. This behavior is sharply contrasted with the slow early-time growth of the analog of the OTOC in the systems{\textquoteright} classical counterparts. These results suggest that classical-to-quantum correspondence in dynamics is violated in the OTOC even before quantum interference develops.}, issn = {0031-9007}, doi = {10.1103/PhysRevLett.125.014101}, author = {Rozenbaume, Efim B. and Bunimovich, Leonid A. and Galitski, Victor} } @article { ISI:000510841200002, title = {Electron-induced massive dynamics of magnetic domain walls}, journal = {Phys. Rev. B}, volume = {101}, number = {5}, year = {2020}, month = {FEB 4}, pages = {054407}, publisher = {AMER PHYSICAL SOC}, type = {Article}, abstract = {We study the dynamics of domain walls (DWs) in a metallic, ferromagnetic nanowire, focusing on inertial effects on the DW due to interaction with a conduction electron bath. We develop a Keldysh collective coordinate technique to describe the effect of conduction electrons on rigid magnetic structures. The effective Lagrangian and Langevin equations of motion for a DW are derived microscopically, including the full response kernel which is nonlocal in time. The DW dynamics is described by two collective degrees of freedom: position and tilt angle. The coupled Langevin equations therefore involve two correlated noise sources, leading to a generalized fluctuation-dissipation theorem (FDT). The DW response kernel due to electrons contains two parts: one related to dissipation via FDT and another reactive part. We prove that the latter term leads to a mass for both degrees of freedom, even though the intrinsic bare mass is zero. The electron-induced mass is present even in a clean system without pinning or specifically engineered potentials. The resulting equations of motion contain rich dynamical solutions and point toward a way to control domain wall motion in metals via the electronic system properties. We discuss two observable consequences of the mass, hysteresis in the DW dynamics, and resonant response to ac current.}, issn = {2469-9950}, doi = {10.1103/PhysRevB.101.054407}, author = {Hurst, Hilary M. and Galitski, Victor and Heikkila, Tero T.} } @article {16686, title = {Many-Body Dynamical Localization in a Kicked Lieb-Liniger Gas}, journal = {Phys. Rev. Lett.}, volume = {124}, year = {2020}, month = {04/2020}, pages = {155302}, abstract = {The kicked rotor system is a textbook example of how classical and quantum dynamics can drastically differ. The energy of a classical particle confined to a ring and kicked periodically will increase linearly in time whereas in the quantum version the energy saturates after a finite number of kicks. The quantum system undergoes Anderson localization in angular-momentum space. Conventional wisdom says that in a many-particle system with short-range interactions the localization will be destroyed due to the coupling of widely separated momentum states. Here we provide evidence that for an interacting one-dimensional Bose gas, the Lieb-Liniger model, the dynamical localization can persist at least for an unexpectedly long time.

}, keywords = {Quantum Physics, Thermodynamics}, doi = {10.1103/PhysRevLett.124.155302}, url = {https://link.aps.org/doi/10.1103/PhysRevLett.124.155302}, author = {Rylands, Colin and Rozenbaum, Efim B. and Galitski, Victor and Konik, Robert} } @article {19051, title = {Many-Body Level Statistics of Single-Particle Quantum Chaos}, journal = {Phys. Rev. Lett.}, volume = {125}, year = {2020}, month = {Dec}, pages = {250601}, doi = {10.1103/PhysRevLett.125.250601}, url = {https://link.aps.org/doi/10.1103/PhysRevLett.125.250601}, author = {Liao, Yunxiang and Vikram, Amit and Galitski, Victor} } @article { ISI:000505981500001, title = {Many-body localization landscape}, journal = {Phys. Rev. B}, volume = {101}, number = {1}, year = {2020}, month = {JAN 6}, pages = {014201}, publisher = {AMER PHYSICAL SOC}, type = {Article}, abstract = {We generalize the notion of {\textquoteleft}{\textquoteleft}localization landscape,{{\textquoteright}{\textquoteright}} introduced by M. Filoche and S. Mayboroda {[}Proc. Natl. Acad. Sci. USA 109, 14761 (2012)] for the single-particle Schrodinger operator, to a wide class of interacting many-body Hamiltonians. The many-body localization landscape (MBLL) is defined on a graph in the Fock space, whose nodes represent the basis vectors in the Fock space and edges correspond to transitions between the nodes connected by the hopping term in the Hamiltonian. It is shown that in analogy to the single-particle case, the inverse MBLL plays the role of an effective potential in the Fock space. We construct a generalized discrete Agmon metric and prove Agmon inequalities on the Fock-state graph to obtain bounds on the exponential decay of the many-body wave functions in the Fock space. The corresponding construction is motivated by the semiclassical WKB approximation, but the bounds are exact and fully quantum mechanical. We then prove a series of locality theorems which establish where in the Fock space we expect eigenstates to localize. Using these results as well as the locator expansion, we establish evidence for the existence of many-body localized states for a wide class of lattice models in any physical dimension in at least a part of their Hilbert space. The key to this argument is the observation that in sharp contrast to the conventional locator expansion for the Green{\textquoteright}s function, the locator expansion for the landscape function contains no resonances. For short-range hopping, which limits the connectivity of the Fock-state graph, the locator series is proven to be convergent and bounded by a simple geometric series. This, in combination with the discrete Agmon-type inequalities and the locality theorems, shows that localization for a fraction of the Hilbert space survives weak interactions and weak hopping at least for some realizations of disorder, but cannot prove or rule out localization of the entire Hilbert space. We qualitatively discuss potential breakdown of the locator expansion in the MBLL for long-range hopping and the appearance of a mobility edge in higher-dimensional theories.}, issn = {2469-9950}, doi = {10.1103/PhysRevB.101.014201}, author = {Balasubramanian, Shankar and Liao, Yunxiang and Galitski, Victor} } @article {rylands_photon-mediated_2020, title = {Photon-{Mediated} {Peierls} {Transition} of a {1D} {Gas} in a {Multimode} {Optical} {Cavity}}, journal = {Phys. Rev. Lett.}, volume = {125}, number = {1}, year = {2020}, note = {Place: ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA Publisher: AMER PHYSICAL SOC Type: Article}, month = {jul}, abstract = {The Peierls instability toward a charge density wave is a canonical example of phonon-driven strongly correlated physics and is intimately related to topological quantum matter and exotic superconductivity. We propose a method for realizing an analogous photon-mediated Peierls transition, using a system of one-dimensional tubes of interacting Bose or Fermi atoms trapped inside a multimode confocal cavity. Pumping the cavity transversely engineers a cavity-mediated metal-to-insulator transition in the atomic system. For strongly interacting bosons in the Tonks-Girardeau limit, this transition can be understood (through fermionization) as being the Peierls instability. We extend the calculation to finite values of the interaction strength and derive analytic expressions for both the cavity field and mass gap. They display nontrivial power law dependence on the dimensionless matter-light coupling.

}, issn = {0031-9007}, doi = {10.1103/PhysRevLett.125.010404}, author = {Rylands, Colin and Guo, Yudan and Lev, Benjamin L. and Keeling, Jonathan and Galitski, Victor} } @article {16911, title = {Photon-Mediated Peierls Transition of a 1D Gas in a Multimode Optical Cavity}, journal = {Phys. Rev. Lett.}, volume = {125}, year = {2020}, month = {Jul}, pages = {010404}, abstract = {The Peierls instability toward a charge density wave is a canonical example of phonon-driven strongly correlated physics and is intimately related to topological quantum matter and exotic superconductivity. We propose a method for realizing an analogous photon-mediated Peierls transition, using a system of one-dimensional tubes of interacting Bose or Fermi atoms trapped inside a multimode confocal cavity. Pumping the cavity transversely engineers a cavity-mediated metal-to-insulator transition in the atomic system. For strongly interacting bosons in the Tonks-Girardeau limit, this transition can be understood (through fermionization) as being the Peierls instability. We extend the calculation to finite values of the interaction strength and derive analytic expressions for both the cavity field and mass gap. They display nontrivial power law dependence on the dimensionless matter-light coupling.

}, doi = {10.1103/PhysRevLett.125.010404}, url = {https://link.aps.org/doi/10.1103/PhysRevLett.125.010404}, author = {Rylands, Colin and Guo, Yudan and Lev, Benjamin L. and Keeling, Jonathan and Galitski, Victor} } @article { ISI:000454906800010, title = {Artificial gauge fields with ultracold atoms}, journal = {PHYSICS TODAY}, volume = {72}, number = {1}, year = {2019}, month = {JAN}, pages = {39-44}, issn = {0031-9228}, doi = {10.1063/PT.3.4111}, author = {Galitski, Victor and Juzeliunas, Gediminas and Ian B Spielman} } @article {ISI:000478991700001, title = {Critical viscosity of a fluctuating superconductor}, journal = {Phys. Rev. B}, volume = {100}, number = {6}, year = {2019}, month = {AUG 2}, pages = {060501}, publisher = {AMER PHYSICAL SOC}, type = {Article}, abstract = {We consider a fluctuating superconductor in the vicinity of the transition temperature, T-c. The fluctuation shear viscosity is calculated. In two dimensions, the leading correction to viscosity is negative and scales as delta eta(T) alpha ln(T - T-c). Critical hydrodynamics of the fluctuating superconductor involves two fluids: a fluid of fluctuating pairs and a quasiparticle fluid of single-electron excitations. The pair viscosity (Aslamazov-Larkin) term is shown to be zero. The (density of states) correction to viscosity of single-electron excitations is negative, which is due to fluctuating pairing that results in a reduction of electron density. Scattering of electrons off of the fluctuations gives rise to an enhanced quasiparticle scattering and another (Maki-Thomson) negative correction to viscosity. Our results suggest that fluctuating superconductors provide a promising platform to investigate low-viscosity electronic media and may potentially host fermionic/electronic turbulence. Some experimental probes of two-fluid critical hydrodynamics are proposed such as time-of-flight measurement of turbulent energy cascades in critical cold atom superfluids and magnetic dynamos in three-dimensional fluctuating superconductors.}, issn = {2469-9950}, doi = {10.1103/PhysRevB.100.060501}, author = {Liao, Yunxiang and Galitski, Victor} } @article {ISI:000476581500009, title = {Evanescent modes and step-like acoustic black holes}, journal = {Ann. Phys.}, volume = {407}, year = {2019}, month = {AUG}, pages = {148-165}, publisher = {ACADEMIC PRESS INC ELSEVIER SCIENCE}, type = {Article}, abstract = {We consider a model of an acoustic black hole formed by a quasi-one dimensional Bose-Einstein condensate with a step-like horizon. This system is analyzed by solving the corresponding Bogoliubov-de Gennes equation with an appropriate matching condition at the jump. When the step is between a subsonic and supersonic flow, a sonic horizon develops and in addition to the scattering coefficients we compute the distribution of the accompanying analogue Hawking radiation. Additionally, in response to the abrupt variation in flow and non-linear Bogoliubov dispersion relation, evanescent solutions of the Bogoliubov-de Gennes equation also appear and decay out from the horizon. We bound this decay length and show that these modes produce a modulation of observables outside the event horizon by their interference with outgoing Hawking flux. We go further and find specific superpositions of ingoing eigenmodes which exhibit coherent cancellation of the Hawking flux outside the horizon but nevertheless have evanescent support outside the black hole. We conclude by speculating that when quasiparticle interactions are included, evanescent modes may yield a leakage of information across the event horizon via interactions between the real outgoing Hawking flux and the virtual evanescent modes, and that we may expect this as a generic feature of models which break Lorentz invariance at the UV (Planck) scale. (C) 2019 Elsevier Inc. All rights reserved.}, keywords = {Acoustic black hole, Analogue gravity, Bogoliubov-de Gennes quasiparticle, Bose-Einstein condensate, Evanescent mode, Hawking radiation}, issn = {0003-4916}, doi = {10.1016/j.aop.2019.04.017}, author = {Curtis, Jonathan and Refael, Gil and Galitski, Victor} } @article {14481, title = {Perfect Andreev reflection due to the Klein paradox in a topological superconducting state}, journal = {Nature}, volume = {570}, year = {2019}, pages = {344{\textendash}348}, abstract = {In 1928, Dirac proposed a wave equation to describe relativistic electrons1. Shortly afterwards, Klein solved a simple potential step problem for the Dirac equation and encountered an apparent paradox: the potential barrier becomes transparent when its height is larger than the electron energy. For massless particles, backscattering is completely forbidden in Klein tunnelling, leading to perfect transmission through any potential barrier2,3. The recent advent of condensed-matter systems with Dirac-like excitations, such as graphene and topological insulators, has opened up the possibility of observing Klein tunnelling experimentally4{\textendash}6. In the surface states of topological insulators, fermions are bound by spin{\textendash}momentum locking and are thus immune from backscattering, which is prohibited by time-reversal symmetry. Here we report the observation of perfect Andreev reflection in point-contact spectroscopy{\textendash}-a clear signature of Klein tunnelling and a manifestation of the underlying {\textquoteleft}relativistic{\textquoteright}physics of a proximity-induced superconducting state in a topological Kondo insulator. Our findings shed light on a previously overlooked aspect of topological superconductivity and can serve as the basis for a unique family of spintronic and superconducting devices, the interface transport phenomena of which are completely governed by their helical topological states.

}, isbn = {1476-4687}, doi = {10.1038/s41586-019-1305-1}, url = {https://doi.org/10.1038/s41586-019-1305-1}, author = {Lee, Seunghun and Stanev, Valentin and Zhang, Xiaohang and Stasak, Drew and Flowers, Jack and Higgins, Joshua S. and Dai, Sheng and Blum, Thomas and Pan, Xiaoqing and Yakovenko, Victor M. and Paglione, Johnpierre and Greene, Richard L. and Galitski, Victor and Takeuchi, Ichiro} } @article {ISI:000475499200001, title = {Universal level statistics of the out-of-time-ordered operator}, journal = {Phys. Rev. B}, volume = {100}, number = {3}, year = {2019}, month = {JUL 15}, pages = {035112}, publisher = {AMER PHYSICAL SOC}, type = {Article}, abstract = {The out-of-time-ordered correlator has been proposed as an indicator of chaos in quantum systems due to its simple interpretation in the semiclassical limit. In particular, its rate of possible exponential growth at h -> 0 is closely related to the classical Lyapunov exponent. Here we explore how this approach to quantum chaos relates to the random-matrix theoretical description. To do so, we introduce and study the level statistics of the logarithm of the out-of-time-ordered operator, (Lambda) over cap (t) = In (-{[}(x) over cap (t),(p) over cap (x)(0)](2) )/(2t), that we dub the {\textquoteleft}{\textquoteleft}Lyapunovian{{\textquoteright}{\textquoteright}} or {\textquoteleft}{\textquoteleft}Lyapunov operator{{\textquoteright}{\textquoteright}} for brevity. The Lyapunovian{\textquoteright}s level statistics is calculated explicitly for the quantum stadium billiard. It is shown that in the bulk of the filtered spectrum, this statistics perfectly aligns with the Wigner-Dyson distribution. One of the advantages of looking at the spectral statistics of this operator is that it has a well-defined semiclassical limit where it reduces to the matrix of uncorrelated classical finite-time Lyapunov exponents in a partitioned phase space. We provide a heuristic picture interpolating these two limits using Moyal quantum mechanics. Our results show that the Lyapunov operator may serve as a useful tool to characterize quantum chaos and in particular quantum-to-classical correspondence in chaotic systems by connecting the semiclassical Lyapunov growth at early times, when the quantum effects are weak, to universal level repulsion that hinges on strong quantum interference effects.}, issn = {2469-9950}, doi = {10.1103/PhysRevB.100.035112}, author = {Rozenbaum, Efim B. and Ganeshan, Sriram and Galitski, Victor} } @article { ISI:000442061000007, title = {Analogue stochastic gravity in strongly-interacting Bose-Einstein condensates}, journal = {ANNALS OF PHYSICS}, volume = {395}, year = {2018}, month = {AUG}, pages = {84-111}, keywords = {Collective modes, General relativity, Quantum fluids, Stochastic dynamics}, issn = {0003-4916}, doi = {10.1016/j.aop.2018.05.009}, author = {Keser, Aydin Cem and Galitski, Victor} } @article {10476, title = {Dynamo Effect and Turbulence in Hydrodynamic Weyl Metals}, journal = {Phys. Rev. Lett.}, volume = {121}, year = {2018}, month = {Oct}, pages = {176603}, doi = {10.1103/PhysRevLett.121.176603}, url = {https://link.aps.org/doi/10.1103/PhysRevLett.121.176603}, author = {Galitski, Victor and Kargarian, Mehdi and Syzranov, Sergey} } @article { ISI:000433419500002, title = {Magnon-induced non-Markovian friction of a domain wall in a ferromagnet}, journal = {PHYSICAL REVIEW B}, volume = {97}, number = {17}, year = {2018}, month = {MAY 30}, pages = {174433}, issn = {2469-9950}, doi = {10.1103/PhysRevB.97.174433}, author = {Kim, Se Kwon and Tchernyshyov, Oleg and Galitski, Victor and Tserkovnyak, Yaroslav} } @article { ISI:000450139700007, title = {Nonlinear sigma model approach to many-body quantum chaos: Regularized and unregularized out-of-time-ordered correlators}, journal = {PHYSICAL REVIEW B}, volume = {98}, number = {20}, year = {2018}, month = {NOV 14}, pages = {205124}, issn = {2469-9950}, doi = {10.1103/PhysRevB.98.205124}, author = {Liao, Yunxiang and Galitski, Victor} } @article {ISI:000393498700001, title = {Dynamical localization of coupled relativistic kicked rotors}, journal = {PHYSICAL REVIEW B}, volume = {95}, number = {6}, year = {2017}, month = {FEB 6}, abstract = {A periodically driven rotor is a prototypical model that exhibits a transition to chaos in the classical regime and dynamical localization (related to Anderson localization) in the quantum regime. In a recent work {[}Phys. Rev. B 94, 085120 (2016)], A. C. Keser et al. considered a many-body generalization of coupled quantum kicked rotors, and showed that in the special integrable linear case, dynamical localization survives interactions. By analogy with many-body localization, the phenomenon was dubbed dynamical many-body localization. In the present work, we study nonintegrable models of single and coupled quantum relativistic kicked rotors (QRKRs) that bridge the gap between the conventional quadratic rotors and the integrable linear models. For a single QRKR, we supplement the recent analysis of the angular-momentum-space dynamics with a study of the spin dynamics. Our analysis of two and three coupled QRKRs along with the proved localization in the many-body linear model indicate that dynamical localization exists in few-body systems. Moreover, the relation between QRKR and linear rotor models implies that dynamical many-body localization can exist in generic, nonintegrable many-body systems. And localization can generally result from a complicated interplay between Anderson mechanism and limiting integrability, since the many-body linear model is a high-angular-momentum limit of many-body QRKRs. We also analyze the dynamics of two coupled QRKRs in the highly unusual superballistic regime and find that the resonance conditions are relaxed due to interactions. Finally, we propose experimental realizations of the QRKR model in cold atoms in optical lattices.}, issn = {2469-9950}, doi = {10.1103/PhysRevB.95.064303}, author = {Rozenbaum, Efim B. and Galitski, Victor} } @article {ISI:000400652700006, title = {Kinetic theory of dark solitons with tunable friction}, journal = {PHYSICAL REVIEW A}, volume = {95}, number = {5}, year = {2017}, month = {MAY 3}, abstract = {We study controllable friction in a system consisting of a dark soliton in a one-dimensional Bose-Einstein condensate coupled to a noninteracting Fermi gas. The fermions act as impurity atoms, not part of the original condensate, that scatter off of the soliton. We study semiclassical dynamics of the dark soliton, a particlelike object with negative mass, and calculate its friction coefficient. Surprisingly, it depends periodically on the ratio of interspecies (impurity-condensate) to intraspecies (condensate-condensate) interaction strengths. By tuning this ratio, one can access a regime where the friction coefficient vanishes. We develop a general theory of stochastic dynamics for negative-mass objects and find that their dynamics are drastically different from their positive-mass counterparts: they do not undergo Brownian motion. From the exact phase-space probability distribution function (i.e., in position and velocity), we find that both the trajectory and lifetime of the soliton are altered by friction, and the soliton can undergo Brownian motion only in the presence of friction and a confining potential. These results agree qualitatively with experimental observations by Aycock et al. {[}Proc. Natl. Acad. Sci. USA 114, 2503 (2017)] in a similar system with bosonic impurity scatterers.}, issn = {2469-9926}, doi = {10.1103/PhysRevA.95.053604}, author = {Hurst, Hilary M. and Efimkin, Dmitry K. and Ian B Spielman and Galitski, Victor} } @article {6621, title = {Lyapunov Exponent and Out-of-Time-Ordered Correlator{\textquoteright}s Growth Rate in a Chaotic System}, journal = {Phys. Rev. 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Rev. Lett.}, volume = {116}, year = {2016}, month = {05/2016}, pages = {225301}, doi = {10.1103/PhysRevLett.116.225301}, url = {http://link.aps.org/doi/10.1103/PhysRevLett.116.225301}, author = {Efimkin, Dmitry K. and Hofmann, Johannes and Galitski, Victor} } @article { ISI:000377796000001, title = {Parity effect in a mesoscopic Fermi gas}, journal = {PHYSICAL REVIEW A}, volume = {93}, number = {6}, year = {2016}, month = {JUN 13}, pages = {061602}, issn = {2469-9926}, doi = {10.1103/PhysRevA.93.061602}, author = {Hofmann, Johannes and Lobos, Alejandro M. and Galitski, Victor} } @article {4416, title = {Radio Frequency Tunable Oscillator Device Based on a SmB6 Microcrystal}, journal = {Phys. Rev. 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