Signatures of a quantum stabilized fluctuating phase and critical dynamics in a kinetically-constrained open many-body system with two absorbing states

TL;DR

This paper explores a quantum many-body system with competing coherent and dissipative processes, revealing a fluctuating phase stabilized by quantum effects and complex critical dynamics near symmetry points, advancing understanding of non-equilibrium quantum phases.

Contribution

It introduces a kinetically constrained quantum model with two absorbing states, demonstrating quantum stabilization of fluctuating phases and novel critical behavior at symmetry points.

Findings

Quantum coherence stabilizes a fluctuating active phase.

Power-law approach to absorbing states with variable exponents.

Complex interplay of symmetry, coherence, and dissipation leads to new non-equilibrium phases.

Abstract

We introduce and investigate an open many-body quantum system in which kinetically constrained coherent and dissipative processes compete. The form of the incoherent dissipative dynamics is inspired by that of epidemic spreading or cellular-automaton-based computation related to the density-classification problem. It features two non-fluctuating absorbing states as well as a $\mathcal{Z}_2$-symmetric point in parameter space. The coherent evolution is governed by a kinetically constrained $\mathcal{Z}_2$-symmetric many-body Hamiltonian which is related to the quantum XOR-Fredrickson-Andersen model. We show that the quantum coherent dynamics can stabilize a fluctuating state and we characterize the transition between this active phase and the absorbing states. We also identify a rather peculiar behavior at the $\mathcal{Z}_2$-symmetric point. Here the system approaches the absorbing-state manifold with a dynamics that follows a power-law whose exponent continuously varies with the relative strength of the coherent dynamics. Our work shows how the interplay between coherent and dissipative processes as well as symmetry constraints may lead to a highly intricate non-equilibrium evolution and may stabilize phases that are absent in related classical problems.