Condensation of phonons in an ultracold Bose gas

TL;DR

This paper investigates how modulating the transverse trap frequency in an ultracold Bose gas induces phonon condensation through parametric resonance, leading to a stationary state with macroscopic phonon occupation.

Contribution

It demonstrates the formation of a phonon condensate in an elongated Bose gas via parametric resonance and nonlinear evolution at zero temperature.

Findings

Phonons can be generated by trap modulation.

A stationary state with macroscopic phonon occupation forms.

Nonlinear interactions stabilize the phonon condensate.

Abstract

We consider the generation of longitudinal phonons in an elongated Bose-condensed gas at zero temperature due to parametric resonance as a result of the modulation of the transverse trap frequency. The nonlinear temporal evolution with account of the phonon-phonon interaction leads self-consistently to the formation of the stationary state with the macroscopic occupation of a single phonon quantum state.