Activity-induced phase transition in a quantum many-body system

TL;DR

This paper introduces a simple quantum many-body model demonstrating activity-induced quantum phase transitions driven by non-Hermiticity, linking classical nonequilibrium kinetics with non-Hermitian quantum physics.

Contribution

It presents a novel quantum model based on classical MIPS that exhibits activity-driven phase transitions, bridging classical kinetics and quantum non-Hermitian physics.

Findings

Quantum phase transitions induced by non-Hermiticity.

Model includes active phases like flocking.

Transitions can be tested in ultracold atom experiments.

Abstract

A crowd of nonequilibrium entities can show phase transition behaviors that are prohibited in conventional equilibrium setups. An interesting question is whether similar activity-driven phase transitions also occur in pure quantum systems. Here we introduce a minimally simple quantum many-body model that undergoes quantum phase transitions induced by non-Hermiticity. The model is based on a classical anisotropic lattice gas model that undergoes motility-induced phase separation (MIPS), and the quantum phase diagram includes other active phases such as the flocking phase. The quantum phase transitions, which in principle can be tested in ultracold atom experiments, is also identified as the transitions of dynamical paths in the classical kinetics upon the application of biasing fields. This approach sheds light on the useful connection between classical nonequilibrium kinetics and non-Hermitian quantum physics.