Decoherent Quench Dynamics across Quantum Phase Transitions

TL;DR

This paper develops a framework to study decoherent quantum quench dynamics across phase transitions, revealing universal power-law scaling behaviors that differ from traditional Kibble-Zurek predictions, demonstrated through topological insulator models.

Contribution

It introduces a generalized decoherent Kibble-Zurek scaling theory applicable to quantum phase transitions with decoherence, supported by numerical simulations.

Findings

Decoherence alters the freeze-out scaling exponents from standard Kibble-Zurek predictions.

Universal power-law scaling of freeze-out time and length with quench rate in decoherent regimes.

Verification of scaling behavior in topological Chern insulator systems.

Abstract

We present a formulation for investigating quench dynamics across quantum phase transitions in the presence of decoherence. We formulate decoherent dynamics induced by continuous quantum non-demolition measurements of the instantaneous Hamiltonian. We generalize the well-studied universal Kibble-Zurek behavior for linear temporal drive across the critical point. We identify a strong decoherence regime wherein the decoherence time is shorter than the standard correlation time, which varies as the inverse gap above the groundstate. In this regime, we find that the freeze-out time $\bar{t}\sim\tau^{{2\nu z}/({1+2\nu z})}$ for when the system falls out of equilibrium and the associated freeze-out length $\bar{\xi}\sim\tau^{\nu/({1+2\nu z})}$ show power-law scaling with respect to the quench rate $1/\tau$, where the exponents depend on the correlation length exponent $\nu$ and the dynamical exponent $z$ associated with the transition. The universal exponents differ from those of standard Kibble-Zurek scaling. We explicitly demonstrate this scaling behavior in the instance of a topological transition in a Chern insulator system. We show that the freeze-out time scale can be probed from the relaxation of the Hall conductivity. Furthermore, on introducing disorder to break translational invariance, we demonstrate how quenching results in regions of imbalanced excitation density characterized by an emergent length scale which also shows universal scaling. We perform numerical simulations to confirm our analytical predictions and corroborate the scaling arguments that we postulate as universal to a host of systems.