Avalanche Instability as Nonequilibrium Quantum Criticality

TL;DR

This paper introduces the concept of avalanche instability as a nonequilibrium quantum critical phenomenon, driven by phonon emission and characterized by a quantum phase transition with reentrant behavior.

Contribution

It presents an analytic and numerical study of quantum avalanche as a new type of nonequilibrium quantum phase transition involving phonon-mediated band collapse.

Findings

Identification of a quantum avalanche transition driven by phonon emission.

Reentrant avalanche domes near the phase boundary.

Temperature dependence confirms the quantum critical nature.

Abstract

A fundamental instability in the nonequilibrium conduction band under a electric field bias is proposed via the spontaneous emission of coherent phonons. Analytic theory, supported by numerical calculations, establishes that the quantum avalanche, an abrupt nonequilibrium occupation of excited bands, results from the competition between the collapse of the band minimum via the phonon emission and the dephasing of the electron with the environment. The continuous avalanche transition is a quantum phase transition with the nonequilibrium phase diagram determined by the avalanche parameter $\beta$, with peculiar reentrant avalanche domes close to the phase boundary. We further confirm the nature of the quantum avalanche with the temperature dependence.