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 B44: Dynamics of Quenched and Driven Quantum Systems ILive
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Sponsoring Units: DCMP Chair: Ettore Vitali, California State University, Fresno |
Monday, March 15, 2021 11:30AM - 11:42AM Live |
B44.00001: Ultrafast dynamics in MnPS3 studied by time-resolved optical spectroscopy Jun-Yi Shan, Mengxing Ye, Hao Chu, Sungmin Lee, Je-Geun Park, Leon Balents, David Hsieh The van der Waals insulator MnPS3 exhibits a magneto-electric type antiferromagnetic order that persists down to the few layer limit. Recently it has been shown that this antiferromagnetic order parameter can be measured using optical second harmonic generation (SHG). In this talk, I will report time-resolved SHG and linear reflectivity measurements on MnPS3, demonstrating ultrafast modulation of its electronic properties via both thermal and non-thermal mechanisms. |
Monday, March 15, 2021 11:42AM - 11:54AM Live |
B44.00002: Second order Josephson effect in excitonic insulators Zhiyuan Sun, Tatsuya Kaneko, Denis Golez, Andrew Millis We show that in electron-hole bilayers with conduction and valence bands formed by atomic orbitals with different parities, nonzero interlayer tunneling leads to a second order Josephson effect in the excitonic insulating state, where the interlayer electrical current is related to the phase of the excitonic order parameter as J = Jc sin(2θ) instead of J = Jc sin(θ). An interlayer voltage rotates the phase in the same way as AC Josephson effect. Suitable voltage pulses can switch the system between the two degenerate ground states with θ=0,π, making it a potentially ultra fast memory device. We also discuss a three dimensional stack of alternating electron-hole layers and a two dimensional stack of electron-hole chains, where the excitonic insulating states exhibit nontrivial topology. |
Monday, March 15, 2021 11:54AM - 12:06PM Live |
B44.00003: Field-Driven Correlated Quantum Systems, Bridging the Gap Between the Transient and the Steady State Eric Dohner, Herbert Fotso, Alexander F Kemper, James Freericks Correlated quantum systems away from equilibrium have rightfully generated a lot of interest. Computational methods play an important role in understanding these systems but they are constrained by difficulties inherent to correlated systems that are exacerbated away from equilibrium. This prevents a full characterization of the dynamics. Previously, a set of relaxation scenarios were identified when systems initially in equilibrium are suddenly driven by a DC electric field. In particular, for certain parameters both the Hubbard and the Falicov-Kimball models evolve monotonically towards infinite temperature steady states that can be fully characterized by formulating solutions directly in the steady state. In the process these systems evolve through successive quasi-thermal states obeying the fluctuation dissipation theorem. We demonstrate an extrapolation scheme that can be leveraged to extend the characterization of the system from equilibrium to steady state at minimal computational cost. Namely, we extrapolate the monotonic temperature of the system and use the fluctuation dissipation theorem to construct the self-energy beyond the transient. All momentum dependent quantities can then be obtained within the DMFT formalism. |
Monday, March 15, 2021 12:06PM - 12:18PM Live |
B44.00004: Measurement Protected Quantum Phases Shengqi Sang, Timothy Hsieh We introduce a class of hybrid quantum circuits, with random unitaries and projective measurements, which host long-range order in the area law entanglement phase of the steady state. Our primary example is circuits with unitaries respecting a global Ising symmetry and two competing types of measurements. The phase diagram has an area law phase with spin glass order, which undergoes a direct transition to a paramagnetic phase with volume law entanglement, as well as a critical regime. Using mutual information diagnostics, we find that such entanglement transitions preserving a global symmetry are in new universality classes. We analyze generalizations of such hybrid circuits to higher dimensions, which allow for coexistence of order and volume law entanglement, as well as topological order without any symmetry restrictions. |
Monday, March 15, 2021 12:18PM - 12:30PM Live |
B44.00005: Systematic large flavor fTWA approach to interaction quenches Alexander Osterkorn, Stefan Kehrein Studying the out-of-equilibrium quantum dynamics in two-dimensional lattice models is challenging due to the lack of a general purpose simulation method. |
Monday, March 15, 2021 12:30PM - 12:42PM Live |
B44.00006: Matrix product state simulations with general non-Abelian symmetries Miklós Antal Werner, Catalin Pascu Moca, Örs Legeza, Gergely Zaránd We introduce the notion of non-Abelian tensors, and use them to build a general non-Abelian matrix product state (NA-MPS) ansatz. We construct a non-Abelian time evolving block decimation (NA-TEBD) scheme that uses an arbitrary number of Abelian and non-Abelian symmetries. Our approach increases the computional efficiency of matrix product state based computations by several orders of magnitudes, and makes large bond dimensions accessible even on simple desktop architectures. We demonstrate our approach by studying post-quench dynamics in the repulsive SU(3) Hubbard model. We determine time evolution of various local operators and correlation functions and find that interactions turn algebraic charge relaxation into exponential, and suppress coherent quantum oscillations rapidly. |
Monday, March 15, 2021 12:42PM - 12:54PM Live |
B44.00007: Femtosecond thermalization of electrons and holes in transition-metal ferromagnets Volodymyr Turkowski, Naseem Ud, Hung-Tzu Chang, Stephen R Leone, Talat S. Rahman We analyze ultrafast charge dynamics in transition metal ferromagnets Fe, Co and Ni by using dynamical mean-field theory and time-dependent density-functional theory (DMFT+TDDFT) . We pay special attention to the ultrafast thermalization of electron and hole subsystems after the system is excited by a few-fs laser pulse. At such a short time scales the only source of scattering is electron-electron interaction. We take into account these effects through a non-collinear TDDFT exchange-correlation kernel derived from the DMFT spin-resolved susceptibility. It is demonstrated that the charge thermalization in all systems happens at time ~10fs. This result is in agreement with available experimental data for Ni. We discuss the differences in charge relaxation in different materials, as well as the difference in the thermalization of electrons and holes. Obtained results may shed light on details of the ultrafast charge and spin dynamics in ferromagnets, including possibility of long-time metastable states and even photoinduced phase transitions. |
Monday, March 15, 2021 12:54PM - 1:06PM Live |
B44.00008: Quantum Wakes in Lattice Fermions Matthew Wampler, Peter Schauss, Eugene Kolomeisky, Israel Klich The wake following a vessel in water is a signature interference effect of moving bodies, and, as described by Lord Kelvin, is contained within a constant universal angle. However, wakes may accompany different kinds of moving disturbances in other situations and even in lattice systems. Here, we investigate the effect of moving disturbances on a Fermi lattice gas of ultracold atoms and analyze the novel types of wake patterns that may occur. We show how at half-filling, the wake angles are dominated by the ratio of the hopping energy to the velocity of the disturbance and on the angle of motion relative to the lattice direction. Moreover, we study the difference between wakes left behind a moving particle detector versus that of a moving potential or a moving particle extractor. We show that these scenarios exhibit dramatically different behavior at half-filling, with the "measurement wake" following an idealized detector vanishing, though the motion of the detector does still leaves a trace through a "fluctuation wake." Finally, we discuss the experimental requirements to observe our predictions in ultracold fermionic atoms in optical lattices. |
Monday, March 15, 2021 1:06PM - 1:18PM Live |
B44.00009: Quantum Impurity Far from Equilibrium: Quantum Transport Through a Dissipative Resonant Level Using DMRG Xin Zhang, Thomas Barthel, Harold U Baranger Using time-dependent matrix product state techniques, we study the quantum transport properties of a dissipative resonant level model, in which a quantum impurity is coupled to two leads and a bosonic bath. Experimentally, this model can be realized by coupling a quantum dot with resistive leads [1]. We focus on the far-from-equilibrium steady states. The non-linear I-V curves and their scaling behavior are presented for different dissipation strengths in the case of both symmetric and asymmetric coupling. In the symmetric setup, a quantum critical point of the two-channel Kondo class is present [2]. To probe properties of the quasiparticle excitations, which can be measured with tunneling spectroscopy, we study the spectral function and shot noise. |
Monday, March 15, 2021 1:18PM - 1:30PM Live |
B44.00010: Logarithmic entanglement growth from disorder-free localisation in the two-leg compass ladder Oliver Hart, Sarang Gopalakrishnan, Claudio Castelnovo We explore the finite-temperature dynamics of the quasi-1D orbital compass and plaquette Ising models. We map these systems onto a model of free fermions coupled to strictly localized spin-1/2 degrees of freedom. At finite temperature the localized degrees of freedom act as emergent disorder and localize the fermions. Although the model can be analyzed using free-fermion techniques, it has dynamical signatures in common with typical many-body localized systems: Starting from generic initial states, entanglement grows logarithmically; in addition, equilibrium dynamical correlation functions decay with an exponent that varies continuously with temperature and model parameters. These quasi-1D models offer an experimentally realizable setting in which natural dynamical probes show signatures of disorder-free localization. |
Monday, March 15, 2021 1:30PM - 1:42PM Live |
B44.00011: Quantum Quenches in Coupled Luttinger Liquids: Truncated Spectrum Approach vs Semi-Classics Robert Konik, Andrew J. A. James, Andrew Hallam We consider a quantum quench of multiple Luttinger liquids. Here we initialize the system by supposing the Luttinger liquids are in their ground state. At t=0 we turn on a tunnel coupling between the liquids. We then study the subsequent time evolution of quantities such as the mode occupation numbers. We show that there are discrepancies between the results as determined by the truncated spectrum approach and a semi-classical treatment. We argue that this difference is real through unitary perturbation theory which is exact at short times. At late times the evolution of the system can be understood through the spectrum of sine-Gordon. We provide evidence that the non-classical part of this spectrum plays a role. We comment on the relevance of these results for experimental quantum quenches on two coupled Luttinger liquids. |
Monday, March 15, 2021 1:42PM - 1:54PM Live |
B44.00012: Hole burning as a probe of localization. Vikram Ravindranath, Sarang Gopalakrishnan, Vadim Oganesyan An ensemble of two level systems (TLS) will, upon driving, generally undergo hole burning, wherein the response of the system to a probe will be suppressed around the frequencies at which it was driven. Many explanations of transport in Anderson Localized systems have relied on treating them as similar ensembles of TLS – an idea that was proposed by Mott. Under such considerations, Anderson Localized systems should also undergo Hole Burning under sustained driving. We have attempted to explore its implications, especially in transport quantities such as the AC conductivity. |
Monday, March 15, 2021 1:54PM - 2:06PM Live |
B44.00013: Quench dynamics of optically pumped electron-phonon systems John Sous, Benedikt Kloss, Dante Kennes, David Reichman, Andrew Millis Motivated by recent experimental reports of novel phases in materials driven by intense radiation fields, we use numerically exact matrix product and exact diagonalization algorithms to simulate the dynamics of a metal driven at t = 0 by a pump that excites dipole-active vibrational modes that are either linearly or quadratically coupled to electrons. We find in certain situations that the electronic properties evolve to a state characterized by a high level of effective spatial disorder. These results have implications to current experiments on pumped metallic crystals. |
Monday, March 15, 2021 2:06PM - 2:18PM Live |
B44.00014: Matrix product state investigations of time-dependent spectral functions after a photoexcitation Constantin Meyer, Salvatore R Manmana We study the time-dependent single-particle spectral function A(k,ω,t) after a photoexcitation of a variant of the 1d Hubbard model with a background staggered magnetic field using matrix product state (MPS) techniques. |
Monday, March 15, 2021 2:18PM - 2:30PM Live |
B44.00015: DC photocurrent in a ferroelectric excitonic insulator Tatsuya Kaneko, Zhiyuan Sun, Yuta Murakami, Denis Golez, Andrew Millis We theoretically investigate the linear and nonlinear optical responses in a non-centrosymmetric excitonic insulator (EI). The ordered state in the EI is characterized by the spontaneous orbital hybridization triggered by the excitonic instability, which can realize electronic ferroelectricity in its EI ground state. We show the optically active collective modes in the linear response regime. Then, using time-dependent mean-field theory, we compute the shift and injection currents as second-order optical responses. We demonstrate that the collective mode of the ferroelectric EI leads to a shift current which shows sharp resonances at sub-bandgap collective mode frequencies. We also find a nonvanishing injection current and discuss its origin associated with optically active collective modes. |
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