Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session F44: Dynamics of Quenched and Driven Quantum Systems IILive
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Sponsoring Units: DCMP Chair: Bowen Shi, University of California, San Diego |
Tuesday, March 16, 2021 11:30AM - 11:42AM Live |
F44.00001: Nonequilibrium phase transition in transport through a driven quantum point contact Oleksandr Gamayun, Artur Slobodeniuk, Jean-Sebastian Caux, Oleg Lychkovskiy We study transport of noninteracting fermions through a periodically driven quantum point contact (QPC) connecting two tight-binding chains. Initially, each chain is prepared in its own equilibrium state, generally with a bias between the chains. We examine the heating rate (or, alternatively, energy increase per cycle) in the nonequilibrium time-periodic steady state established after initial transient dynamics. We find that the heating rate vanishes identically when the driving frequency exceeds the bandwidth of the chain. We first establish this fact for a conformal QPC where the heating rate can be calculated analytically. Then we verify numerically that this nonequilibrium phase transition is present for a generic QPC. Finally, we derive this effect perturbatively in leading order for cases when the QPC Hamiltonian can be viewed as a small perturbation. Strikingly, we discover that for certain QPCs the current averaged over the driving cycle also vanishes above the critical frequency, despite a persistent voltage bias. This shows that a driven QPC can act as a frequency-controlled quantum valve. |
Tuesday, March 16, 2021 11:42AM - 11:54AM Live |
F44.00002: Spatio-temporal Dynamics of Non-equilibrium Phase Separation in Resistive Switching Kunal Mozumdar, Ishiaka Mansaray, Jong E Han We study numerically, the spatio-temporal dynamics of the insulator and metal phases during Mott transition using a novel non-equilibrium free energy technique, developed in an earlier study[1] , and combining it with the resistor network approach to explore electric field driven resistive switching (RS) in a 2D sample. Free-energy approach helps us simulate a Mott Transition on microscopic level without having to specify the exact mechanism behind the switch to be thermal or electronic. Our objective is to characterize the dynamics of the system in its coexistence phase by studying the fluctuations near the critical point. Our study highlights that non-equilibrium dynamics of conducting filament and the internal electric field have a direct free-energy interpretation. We characterize the temporal fluctuations of the resistance using the power spectrum density. Resistance fluctuation of the system has a ∼1/f 2 behavior near the critical point. |
Tuesday, March 16, 2021 11:54AM - 12:06PM Live |
F44.00003: Fast Nonequilibrium Green Functions simulations with GW selfenergies Christopher Makait, Niclas Schlünzen, Jan-Philip Joost, Michael Bonitz Quantum kinetic approaches [1] have proven successful in describing dynamics of the uniform electron gas. The Nonequilibrium Green Functions (NEGF) method is a powerful tool to compute time-dependent expectation values of single-particle observables in correlated quantum many-body-systems. Its unfavorable Nt3 scaling with propagation time Nt could be reduced to Nt2 by introduction of the Generalized Kadanoff-Baym Ansatz (GKBA)[2]. Recently, an exact time-local (Nt1) reformulation of the GKBA, the G1–G2 scheme [3,4], has been found for various self energies, which makes this method viable for long time simulations. |
Tuesday, March 16, 2021 12:06PM - 12:18PM Live |
F44.00004: Quantum supremacy and quantum phase transitions Supanut Thanasilp, Jirawat Tangpanitanon, Marc-Antoine Lemonde, Ninnat Dangniam, Dimitris Angelakis Demonstrating the ability of existing quantum devices to perform certain computational tasks intractable to classical computers represents a cornerstone in quantum computing. Despite the growing number of proposed "quantum supreme'' tasks, it remains an important challenge to find their direct applications. In this work, we describe how the experiment proposed in Ref. [1] to demonstrate quantum supremacy in generic driven many-body systems can be extended to probe quantum phase transitions. We show how key quantum supremacy signatures, such as the distance between the output distribution and Porter Thomas distribution, can be used as order parameters. We apply this approach to a periodically driven disordered 1D Ising chain and show that we can capture the transition between the driven thermalized and many-body localized phases. The transition towards the Floquet prethermalized regime for high-frequency driving is also captured. Revisiting quantum phases of matter in the context of quantum supremacy draws additional links between complexity theory and many-body systems. |
Tuesday, March 16, 2021 12:18PM - 12:30PM Live |
F44.00005: Random multipolar driving: tunably slow heating through spectral engineering Hongzheng Zhao, Florian Mintert, Roderich Moessner, Johannes Knolle We study heating in interacting quantum many-body systems driven by random sequences with n−multipolar correlations, corresponding to a polynomially suppressed low frequency spectrum. For n ≥ 1, we find a prethermal regime, the lifetime of which grows algebraically with the driving rate, with exponent 2n + 1. A simple theory based on Fermi’s golden rule accounts for this behaviour. The quasiperiodic Thue-Morse sequence corresponds to the n →∞ limit, and accordingly exhibits an exponentially long-lived prethermal regime. Despite the absence of periodicity in the drive, and in spite of its eventual heat death, the prethermal regime can host versatile non-equilibrium phases, which we illustrate with a random multipolar discrete time crystal. |
Tuesday, March 16, 2021 12:30PM - 12:42PM Live |
F44.00006: Untangling time scales in entanglement growth in the disordered Fermi Hubbard model Rachel Wortis, Brandon Leipner-Johns Many-body localization impedes the spread of information encoded in initial conditions, providing a intriguing counter point to continuing efforts to understand the approach of quantum systems to equilibrium and also opening the possibility of diverse non-equilibrium phases. While much work in this area has focused on systems with a single degree of freedom per site, motivated by rapid developments in cold atom experiments, we focus on the Fermi Hubbard model, with both spin and charge degrees of freedom. To explore the spread of information between these in the presence of disorder, we compare the time dependence of the entanglement entropy with the time dependence of the charge and spin correlations, and in addition we rewrite the Hamiltonian in terms of charge and spin-specific integrals of motion, allowing us to distinguish time scales associated with charge-charge, spin-spin, and charge-spin correlations. |
Tuesday, March 16, 2021 12:42PM - 12:54PM Live |
F44.00007: Signatures of ultrafast reversal of excitonic order in Ta2NiSe5 Honglie Ning, Omar Mehio, Michael Buchhold, Takashi Kurumaji, Gil Refael, Joseph Checkelsky, David Hsieh In the presence of electron-phonon coupling, an excitonic insulator can harbor two degenerate ground states described by an Ising-type order parameter. Starting from a microscopic Hamiltonian, we derive the equations of motion for the electronic and structural order parameters in the excitonic insulator Ta2NiSe5. We show that the excitonic order can be controllably reversed with appropriate laser excitation sequences. Using a combination of theory and coherent phonon spectroscopy measurements, we report evidence of such reversal in Ta2NiSe5. Our work expands the field of ultrafast order parameter control beyond conventional spin and charge ordered materials. |
Tuesday, March 16, 2021 12:54PM - 1:06PM Live |
F44.00008: Engineering effective adiabatic evolution via suitable coupling to auxiliary systems Rafael Hipolito, Paul Mark Goldbart A quantum system driven by a time-dependent Hamiltonian H0(t) can be engineered to evolve adiabatically [with respect to H0(t)] by the addition of a counterdiabatic term H1(t), as shown by Berry. The time dependence of H0(t) gives rise to a curvature term in the comoving frame, described via a gauge field, that induces transitions between distinct states and whose influence is exactly cancelled byH1(t) . Implementation of H1(t) can be impractical, e.g., because H1(t) is nonlocal. By using geometrical arguments, we explore alternative means to engineer adiabatic evolution via increasing the number of freedoms, and thus induce adiabatic evolution by using entirely local terms. As a specific example, we consider a system of locally interacting particles, for which we wish to engineer adiabatic evolution. We show that by coupling this system to an auxiliary one, we can achieve adiabatic evolution and maintain locality at the expense of increasing the number of degrees of freedom. We explore the required compatibility relations between the original and auxiliary systems and their couplings, and comment on their geometrical significance. |
Tuesday, March 16, 2021 1:06PM - 1:18PM Live |
F44.00009: Decoherent quantum critical quench dynamics in topological phases Wei-Ting Kuo, Yizhuang You, Daniel Arovas, Smitha Vishveshwara We consider the problem of a quench across a quantum phase transition in open quantum systems, and the consequences of its associated non-equilibrium dynamics. We develop a framework for describing quantum critical quenches in the presence of decoherence. We reconstruct the regular Kibble-Zurek scaling for weak decoherence and find new emergent scaling behavior in strong decoherence limit. To investigate the scaling in topological systems, we compute quench-dependent Hall conductance, an experimentally measurable topological response. During the decoherent quench across the critical point, the Hall conductance exhibits a logarithmic divergence at the critical point and a power-law decaying tail in the late duration of the quench process. As a function of quench rate, the power-law decaying timescale follows different scaling based on the strength of the decoherence. |
Tuesday, March 16, 2021 1:18PM - 1:30PM Live |
F44.00010: Fragmentation and glassy dynamics in frustrated spin models with kinematic constraints Kyungmin Lee, Arijeet Pal, Hitesh Changlani Constrained dynamics due to frustration can give rise to glassy behavior in many-body systems. Typical quantum many-body systems thermalize on short time scales independent of the initial condition. However, recent developments show that a large class of systems either do not thermalize or relax anomalously slow for certain initial states, falling outside the rubric of eigenstate thermalization hypothesis. In clean systems, kinematic constraints can lead to Hilbert space fragmentations where certain states fail to reach the thermal steady state. We show that such fragmentation naturally arises in frustrated magnets with low-energy “ice manifolds,” which give rise to a broad range of relaxation time scales. Focusing on kagome lattice, we explicitly show the fragmentation in the Balents-Fisher-Girvin Hamiltonian and a three-coloring model with loop excitations, both with constrained Hilbert spaces. We study their level statistics and relaxation dynamics to develop a coherent picture of glassiness in various limits of the XXZ model on the kagome lattice. |
Tuesday, March 16, 2021 1:30PM - 1:42PM Live |
F44.00011: Engineering Magnetic Phases Out of Equilibrium in a Strongly Spin-Orbit Coupled Honeycomb Magnet Adithya Sriram, Martin Claassen Strongly spin-orbit coupled quantum magnets such as α-RuCl3 and Na2IrO3 have garnered much attention as possible candidates for realizing a Kitaev spin liquid. Although these materials instead display magnetic order at low temperatures, here we show that irradiation with circularly polarized light can provide a new handle to engineer their competing isotropic and anisotropic magnetic interactions and realize this long sought-after phase. Furthermore, we report that direct consideration of ligand-mediated exchange reveals that the combination of time-reversal symmetry breaking and strong spin-orbit interactions allow for the electron spin degree of freedom to couple to the electric field of the drive causing a weak spin-polarization effect similar to that caused by a magnetic field in the [111] direction. The resultant dynamics can be modeled by an extended Heisenberg-Kitaev model in a magnetic field with photo-induced phases determined by pump parameter dependent magnetic interactions. Our results demonstrate a possible pathway towards realizing the elusive Kitaev spin liquid phase as well as predict a novel magnetoelectric coupling effect arising as a consequence of strong spin-orbit coupling and broken time-reversal symmetry. |
Tuesday, March 16, 2021 1:42PM - 1:54PM Live |
F44.00012: Non-Gaussian work statistics in fermionic nanostructures András Grabarits, Marton Kormos, Izabella Lovas, Gergely Zarand We investigate the statistical properties of work performed on generic disordered fermionic nanograins under the effect of external fields during non-equilibrium quantum quenches. We construct a simple mean field theory yielding amazingly precise analytic expressions for the distribution of work in the case of zero temperature for arbitrarily fast driven quantum systems. The tail of the work distribution for large work is found to decay exponentially rather than being Gaussian. Using an effective temperature formalism, we obtain an analytic expression for the work statistics for large enough injected works via bosonization. We compare our predictions with numerical simulations in a 2D hopping model with random on-site energies, finding remarkable agreement. |
Tuesday, March 16, 2021 1:54PM - 2:06PM Live |
F44.00013: Interface Pinning and an Entanglement Transition in Weakly-Monitored Quantum Dynamics Sagar Vijay, Yaodong Li, Matthew P A Fisher Weakly-monitored quantum dynamics -- involving local unitary evolution and infrequent projective measurements -- are known to produce volume-law entangled steady-states that are good at "hiding" local quantum information. Here we show that transitions between this phase, and a phase in which the steady-state resembles a more conventional, volume-law entangled (Page) state can arise in local, weakly-monitored dynamics. We argue that in one spatial dimension, this transition is related to a "pinning" phase transition for a directed polymer in a random environment and in the presence of an attractive interface. We compare our predictions for the critical scaling of the entanglement and for certain properties of the two phases in this setting to results obtained from large-scale numerical simulations of the transition in Clifford circuit dynamics. We also discuss predictions for this phase transition in higher dimensions, and how the classical descriptions of these entanglement transitions can also be used to understand the effects of "unrecorded" measurements on the entanglement growth in quantum many-body dynamics. |
Tuesday, March 16, 2021 2:06PM - 2:18PM On Demand |
F44.00014: Numerical study on quantum transport with strongly interacting fermions Jie Zou, Xiaopeng Li Quantum many-body dynamics in controllable quantum systems has received considerable efforts in recent years.Transport properties in strongly interacting Fermi gas have been investigated in cold atom experiments. The observed experimental phenomena are extremely difficult to simulate in numerical studies. Here, we study one-dimensional spinless fermions at strong interaction limit, and develop an efficient algorithm to simulate the interacting quantum dynamics in this system, by which hundreds to thousands of atoms can be simulated. Despite the present strong interaction, we find that the system exhibits ballistic transport, yet with the propagating velocity strongly renormalized. |
Tuesday, March 16, 2021 2:18PM - 2:30PM On Demand |
F44.00015: Dynamical Transition for a class of integrable models coupled to a bath MADHUMITA SARKAR We study the dynamics of correlation functions of a class of d−dimensional integrable models coupled linearly to a fermionic or bosonic bath in the presence of a periodic drive. In the absence of the bath, these models exhibit a dynamical phase transition; all correlators decay to their steady state values as n^{−(d+2)/2}[n^{−d/2}] above [below] a critical frequency ω_c, where n_0 is the number of drive cycles. We find that the presence of a linearly coupled fermionic bath which maintains integrability of the system preserves this transition. We provide a semi-analytic expression for the evolution operator for this system and use it to provide a phase diagram showing the different dynamical regimes as a function of the system-bath coupling strength and the bath parameters. In contrast, when such models are coupled to a bosonic bath which breaks integrability of the model, we find exponential decay of the correlators to their steady state. Our numerical analysis shows that this exponential decay sets in above a critical number of drive cycles n_c which depends on the system-bath coupling strength and the amplitude of perturbation. Below n_c, the system retains the power-law behavior identical to that for the closed integrable models and the dynamical transition survives. |
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