New kind of condensation of Bose particles through stimulated processes

TL;DR

This paper introduces a novel condensation mechanism for Bose particles driven by stimulated scattering, leading to occupation of excited states without thermalization, conserving particle number and energy.

Contribution

It presents a new type of Bose condensation caused by stimulated processes, distinct from traditional thermalization-based Bose-Einstein condensation.

Findings

Condensation into excited collective states occurs via stimulated scattering.

Total particle number and energy are conserved during the process.

Condensation onset is marked by a critical occupation number overcoming spectral broadening.

Abstract

We show that stimulated scattering of an isolated system of N Bose particles with initially broad energy distribution can yield condensation of particles into excited collective state in which most of the bosons occupy one or several modes. During condensation, the total particle number and energy are conserved, while entropy of the system grows. Onset of condensation occurs at a critical particle occupation number when spectrum narrowing due to stimulated processes overcomes spectrum broadening due to diffusion. This differs from Bose-Einstein condensation in which particles undergo condensation into the equilibrium state due to thermalization processes.