Persistent Hall response in a quantum quench

TL;DR

This paper demonstrates that out-of-equilibrium quantum systems can sustain a persistent Hall response after a quench, revealing novel dynamics and symmetry effects that differ from equilibrium behavior, with potential experimental applications.

Contribution

It uncovers a persistent Hall effect in out-of-equilibrium states post-quench, driven by non-linear response processes, and proposes realizations in Dirac systems for experimental detection.

Findings

Persistent Hall response exists long after a quench.

The effect persists even with time-reversal symmetric Hamiltonians.

Sensitivity to symmetry breaking makes it a diagnostic tool.

Abstract

Out-of-equilibrium systems can host phenomena that transcend the usual restrictions of equilibrium systems. Here we unveil how out-of-equilibrium states, prepared via a quantum quench, can exhibit a non-zero Hall-type response that persists at long times, and even when the instantaneous Hamiltonian is time reversal symmetric; both these features starkly contrast with equilibrium Hall currents. Interestingly, the persistent Hall effect arises from processes beyond those captured by linear response, and is a signature of the novel dynamics in out-of-equilibrium systems. We propose quenches in two-band Dirac systems as natural venues to realize persistent Hall currents, which exist when either mirror or time-reversal symmetry are broken (before or after the quench). Its long time persistence, as well as sensitivity to symmetry breaking, allow it to be used as a sensitive diagnostic of the complex out-equilibrium dynamics readily controlled and probed in cold-atomic optical lattice experiments.