Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session G33: Floquet Systems |
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Sponsoring Units: DCMP Chair: Nishant Agarwal, University of Massachusetts Lowell Room: Room 225 |
Tuesday, March 7, 2023 11:30AM - 11:42AM |
G33.00001: Universality classes of thermalization for mesoscopic Floquet systems Alan Morningstar, David A Huse, Vedika Khemani We identify several distinct phases of thermalization that can occur in Floquet, i.e., periodically driven, many-body quantum chaotic systems. These phases are representative of regimes of behavior in mesoscopic systems, but they are sharply defined in a particular large-system limit where the drive frequency $omega$ scales up with system size N as the usual large-N limit is taken. Thus, we produce a thermalization phase diagram that is relevant for numerical and experimental studies of finite Floquet systems. The phases can be coarsely classified by whether or not the system irreversibly exchanges energy of order $omega$ with the drive, i.e., Floquet thermalizes. Systems that do Floquet thermalize can be further classified based on the Floquet thermal ensemble that describes their final equilibrium, and we show that in most of the phase diagram where Floquet thermalization does occur, the final equilibrium is not a featureless ``infinite-temperature" state. We show that the transition where Floquet thermalization breaks down happens at an extensive drive frequency, and beyond that, further classification of systems that do not Floquet thermalize is based on the presence or absence of rare resonances. Our general theoretical arguments are supported with numerical simulations of a model system. We also simulate an experiment that can be realized on current quantum simulation platforms, that shows Floquet thermalization to a state that is a superposition of distinct temperatures. |
Tuesday, March 7, 2023 11:42AM - 11:54AM |
G33.00002: Emergent Floquet ground state Tatsuhiko N Ikeda, Anatoli S Polkovnikov, Sho Sugiura Periodically driven quantum systems have attracted much attention in view of Floquet engineering, i.e., creating useful effective Hamiltonians by designing appropriate drivings. However, it remains nontrivial how to make their ground states in order to access useful functionalities of the effective Hamiltonians. Also, even if being created, such states are believed to break down eventually due to heating accompanied by external drivings according to the Floquet eigenstate thermalization hypothesis (ETH). |
Tuesday, March 7, 2023 11:54AM - 12:06PM |
G33.00003: Influence matrix, temporal entanglement and efficient simulation of many-body dynamics Michael Sonner, Alessio Lerose, Julian Thoenniss, Dmitry A Abanin Describing dynamics of quantum many-body systems is |
Tuesday, March 7, 2023 12:06PM - 12:18PM |
G33.00004: Periodically Driven Spin-1/2 XXZ Antiferromagnetic Chains Sebastian Eggert, Imke Schneider, ASLAM PARVEJ Time-periodically driven quantum systems are of great interest due the possibility of unconventional states of matter and Floquet engineering. The interplay of many-body interactions and time-periodic manipulations facilitate new phenomena in the steady state. We analyze the Floquet steady states of finite spin-1/2 XXZ antiferromagnetic chains with periodically driven anisotropy parameter at frequencies below the band width, so that resonances are in principle possible. We use a numerical real-time approach with an adiabatic time-evolution protocol by ramping up the driving amplitude of the external periodic drive to prepare a nonequilibrium Floquet steady state. Parametric resonances are expected when the driving frequencies are equal to twice the energy gaps in a finite system. However, the observed resonance absorption of energy and heating is surprisingly weak in our system even for large driving amplitude. This changes if a square wave is used for driving. |
Tuesday, March 7, 2023 12:18PM - 12:30PM |
G33.00005: Matrix product operator approach to nonequilibrium Floquet steady states Zihan Cheng We present a numerical method to simulate nonequilibrium Floquet steady states of one-dimensional periodically-driven (Floquet) many-body systems coupled to a dissipative bath, dubbed open-system Floquet density matrix renormalization group (OFDMRG). This method is based on a matrix product operator ansatz for the Floquet density matrix in frequency-space, and enables access to large systems beyond the reach of exact master equation or quantum trajectory simulations, while retaining information about the periodic micromotion in Floquet steady states. An excited-state extension of this technique also allows computation of the dynamical approach to the steady state on asymptotically long timescales. We benchmark the OFDMRG approach with a driven-dissipative Ising model, and apply it to study the possibility of dissipatively stabilizing pre-thermal discrete time-crystalline order by coupling to a cold bath. |
Tuesday, March 7, 2023 12:30PM - 12:42PM |
G33.00006: Fisher zeros and persistent temporal oscillations in nonunitary quantum circuits Christopher A Hooley, Sankhya Basu, Daniel P Arovas, Sarang Gopalakrishnan, Vadim Oganesyan We present a quantum circuit with measurements and postselection that exhibits a panoply of space- and/or time-ordered phases from ferromagnetic order to spin-density waves to time crystals. Unlike the time crystals that have been found in unitary models, those that occur here are incommensurate with the drive frequency. The period of the incommensurate time-crystal phase may be tuned by adjusting the circuit parameters. We demonstrate that the phases of our quantum circuit, including the inherently nonequilibrium dynamical ones, correspond to complex-temperature equilibrium phases of the exactly solvable square-lattice anisotropic Ising model. |
Tuesday, March 7, 2023 12:42PM - 12:54PM |
G33.00007: Observation of a critical prethermal discrete time crystal created by two-frequency driving William S Beatrez, Arjun Pillai, Otto Janes, Dieter Suter, Ashok Ajoy We report the observation of long-lived Floquet prethermal discrete time crystalline (PDTC) order in a three- dimensional position-disordered lattice of interacting dipolar-coupled 13C nuclei in diamond at room temperature. We demonstrate a novel strategy of "two-frequency" driving, involving an interleaved application of slow and fast drives that simultaneously prethermalize the spins with an emergent quasi-conserved magnetization along the x-axis, while enabling continuous and highly resolved observation of their dynamic evolution when periodically kicked away from x. The PDTC order manifests itself in a robust period doubling response of this drive-induced quasi-conserved spin magnetization interchanging between x and -x; our experiments allow a unique means to study the formation and melting of PDTC order. We obtain movies of the time-crystalline response with a clarity and throughput orders of magnitude greater than previous experiments. We report a PDTC lifetime of 4.68 s (corresponding to 149 Floquet cycles), comparable to state-of-the-art discrete time crystal experiments, and which we measure in a single-shot experiment. Such rapid measurement enables detailed characterization of the entire PDTC phase diagram, rigidity and lifetime, informing on the role of prethermalization towards stabilizing the DTC response. The two-frequency drive approach represents the simplest generalization of DTCs to multi-frequency drives; it expands the toolkit for realizing and investigating long-lived non-equilibrium phases of matter stabilized by emergent quasi-conservation laws. |
Tuesday, March 7, 2023 12:54PM - 1:06PM |
G33.00008: Robust Oscillations and Edge Modes in Nonunitary Floquet Systems Vikram Ravindranath, Xiao Chen We explore oscillatory behaviour in a family of periodically driven spin chains which are subject to a weak measurement followed by post-selection. We discover a transition to an oscillatory phase with half the periodicity of the driving as the strength of the measurement is increased. By mapping these spin chains to free fermion models, we find that this transition is reflected in the opening of a gap in the imaginary direction. Interestingly, we find a robust, purely real, edge π-mode in the oscillatory phase. We establish a correspondence between the complex bulk spectrum and these edge modes. This transition is further found to coincide with a transition in the entanglement scaling of the steady state. These oscillations are numerically found to be stable against interactions and disorder. |
Tuesday, March 7, 2023 1:06PM - 1:18PM |
G33.00009: Engineering critical correlations in uncorrelated thermal states using stochastic driving Armin Rahmani Nonequilibrium quantum dynamics can give rise to the emergence of novel steady states. We propose a scheme for driving an initially uncorrelated thermal state to generate customized correlation functions by determining and reverse engineering the steady-state two-point functions for a class of Markov processes. We also extend the formalism to the calculation of four-point functions. We then apply our method to generating power-law correlated fermionic Green's functions. Furthermore, we find that the power-law patterns emerge at much shorter times than the convergence to the steady state, at which point the disorder in the two-point correlations disappears. On the other hand, the density-density correlations exhibit steady-state disorder while following a power-law trendline. These ideal steady states appear as intermediate-time quasi-steady states in the presence of perturbations. |
Tuesday, March 7, 2023 1:18PM - 1:30PM |
G33.00010: Magnetic sensing employing non-equilibrium long-lived coherences in driven quantum spin ensembles Viatcheslav V Dobrovitski, Will Schenken, Simon A Meynell, Ania C Bleszynski Jayich Ensembles of interacting quantum spins, driven by imperfect control pulses, often demonstrate non-equilibrium coherence that survives far beyond the "usual" decay time, i.e. beyond the Hahn echo decay time [1,2]. This effect occurs in various spin systems of different dimensionalities. The long-lived coherences arise due to accumulation of the control imperfections and inter-spin couplings; they are very robust, and can extend the coherence time by up to five orders of magnitude. |
Tuesday, March 7, 2023 1:30PM - 1:42PM Author not Attending |
G33.00011: Photo-Induced Floquet Effects in Semiconductor Excitons Hossein Dehghani, Mohammad Hafezi Recently, Floquet band engineering has emerged as a new approach to manipulate the properties of solid state systems. A prominent example of such investigations is creating non-trivial topological effects using Floquet physics. However, usually in such studies the presence of Coulomb interaction that can lead to important interacting phenomena such as the presence of bound states is ignored. In this work, we consider a driven semiconductor in the presence of strong Coulomb interactions with a weak coupling to a thermal reservoir. Using a rotating wave approximation to Bethe-Salpeter equations, we study the formation of excitonic quasiparticles in this system and in particular, we calculate the excitons' spectrum as a function of the frequency and amplitude of the drive. We compare our results with conventional non-driven excitons and we propose experimental features to detect the new physics found here.
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Tuesday, March 7, 2023 1:42PM - 1:54PM |
G33.00012: Optical Conductivity Signatures of Floquet Electronic Phases Andrew Cupo, Joshuah T Heath, Emilio Cobanera, James D Whitfield, Chandrasekhar Ramanathan, Lorenza Viola The Floquet graphene antidot lattice is a hole-patterned graphene sheet driven periodically by electromagnetic radiation. Notably, the equilibrium semiconducting state in such a system can be steered through Floquet Dirac, selectively dynamically localized, or Floquet semi-Dirac electronic phases by applying circularly polarized near-IR radiation of suitable intensity [1]. We show that these features persist when the Dirac Hamiltonian approach we previously employed is upgraded to a tight binding model containing all 870 atoms in the supercell, with electromagnetic driving included via the Peierls substitution. In our analysis, we implement a gauge invariant procedure for reducing the full time-dependent Hamiltonian, current, and inverse effective mass operators to an effective four band model, enabling the efficient calculation of the low energy non-equilibrium properties for large nanostructures. On the basis of a Floquet formulation of linear response theory [2], the real and imaginary parts of the longitudinal and transverse components of the probe-frequency-dependent conductivity are computed and correlated with features in the band structures. In practice, the optical conductivity can be connected to the reflectance which, for 2D materials, can be determined experimentally using ellipsometry techniques [3]. |
Tuesday, March 7, 2023 1:54PM - 2:06PM |
G33.00013: The Layered Fermi Surface State: a new non-equilibrium state of quantum matter Inti A Sodemann Villadiego, Oles Matsyshyn, Li-kun Shi, Justin Song Quantum systems that are periodically driven in time can display striking phenomena with no counterparts in equilibrium. A route to realize non-trivial steady states is to couple these systems to a heat bath to avoid the thermal death towards infinite temperature. We will show that a system of fermions driven by an oscillating electric field and coupled to an ideal thermodynamic heat bath, can realize a new universality class of non-equilibrium states in which the fermi surface is fragmented into several layers and which we call the "Layered Fermi Surface State". We develop a theory of universal measurable quantities of this state, such as its quantum oscillations in magnetic fields, its specific heat, and its lesser Green's function (which can be probed in time resolved ARPES) and discuss its potential realization in materials. |
Tuesday, March 7, 2023 2:06PM - 2:18PM |
G33.00014: Simple Model for Memory in Cyclically Sheared Amorphous Materials Siddharth Mansingh, Karin A Dahmen Amorphous materials, when periodically sheared, self organize after a few iterations to reach a limit cycle, thereby encoding memory of the driving amplitude. |
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