Formation of a condensed state with macroscopic number of phonons in ultracold Bose gases

TL;DR

This paper proposes a mechanism for creating a new stationary state with a large number of phonons in ultracold Bose gases, achieved through parametric resonance induced by trap modulation.

Contribution

It introduces a novel method for generating a macroscopic phonon population via parametric resonance in elongated traps, highlighting phonon-phonon interactions and self-consistent evolution.

Findings

Macroscopic phonon states can be formed through trap modulation.

Phonon levels shift to the edge of the amplification interval.

Other levels end with zero population after evolution.

Abstract

A mechanism for the formation of a new type of stationary state with macroscopical number of phonons in condensed atomic gases is proposed. This mechanism is based on generating longitudinal phonons as a result of parametric resonance caused by a permanent modulation of the transverse trap frequency in an elongated trap. The phonon-phonon interaction predetermines the self-consistent evolution which is completed with macroscopic population of one from all levels within the energy interval of parametric amplification. This level proves to be shifted to the edge of this interval. All other levels end the evolution with zero population.