On the number of Bose-selected modes in driven-dissipative ideal Bose gases

TL;DR

This paper investigates how the number of Bose-selected modes in driven-dissipative ideal Bose gases depends on system properties and environment coupling, revealing different behaviors from condensation to high-temperature states.

Contribution

It systematically analyzes the dependence of Bose-selected modes on various classes of rate matrices in driven-dissipative Bose gases, a topic not fully understood before.

Findings

Number of Bose-selected states varies with system-environment coupling.

Different classes of rate matrices lead to distinct Bose selection behaviors.

The study provides a unified framework for understanding Bose selection in non-equilibrium systems.

Abstract

In an ideal Bose gas that is driven into a steady state far from thermal equilibrium, a generalized form of Bose condensation can occur. Namely, the single-particle states unambiguously separate into two groups: the group of Bose-selected states, whose occupations increase linearly with the total particle number, and the group of all other states whose occupations saturate [Phys. Rev. Lett. 111, 240405 (2013)]. However, so far very little is known about how the number of Bose-selected states depends on the properties of the system and its coupling to the environment. The answer to this question is crucial since systems hosting a single, a few, or an extensive number of Bose-selected states will show rather different behavior. While in the former two scenarios each selected mode acquires a macroscopic occupation, corresponding to (fragmented) Bose condensation, the latter case rather bears resemblance to a high-temperature state of matter. In this paper, we systematically investigate the number of Bose-selected states, considering different classes of the rate matrices that characterize the driven-dissipative ideal Bose gases in the limit of weak system-bath coupling. These include rate matrices with continuum limit, rate matrices of chaotic driven systems, random rate matrices, and rate matrices resulting from thermal baths that couple to a few observables only.