Emergent Kardar-Parisi-Zhang phase in quadratically driven condensates

TL;DR

This paper demonstrates that in two-dimensional driven-dissipative bosonic systems, the expected Ising transition is replaced by a nonequilibrium phase exhibiting KPZ physics, with quadratic drive enhancing KPZ scaling visibility.

Contribution

It reveals how nonequilibrium fluctuations suppress the Ising transition and induce KPZ physics in driven-dissipative condensates, highlighting the role of quadratic drive in this process.

Findings

Suppression of Ising phase in 2D driven-dissipative Bose systems.

Emergence of KPZ physics due to strong fluctuations.

Quadratic drive enhances KPZ scaling visibility.

Abstract

In bosonic gases at thermal equilibrium, an external quadratic drive can induce a Bose-Einstein condensation described by the Ising transition, as a consequence of the explicitly broken U(1) phase rotation symmetry down to $\mathbb{Z}_2$. However, in physical realizations such as exciton-polaritons and nonlinear photonic lattices, thermal equilibrium is lost and the state is rather determined by a balance between losses and external drive. A fundamental question is then how nonequilibrium fluctuations affect this transition. Here, we show that in a two-dimensional driven-dissipative Bose system the Ising phase is suppressed and replaced by a nonequilibrium phase featuring Kardar-Parisi-Zhang (KPZ) physics. Its emergence is rooted in a U(1)-symmetry restoration mechanism enabled by the strong fluctuations in reduced dimensionality. Moreover, we show that the presence of the quadratic drive term enhances the visibility of the KPZ scaling, compared to two-dimensional U(1)-symmetric gases, where it has remained so far elusive.