Anharmonicity-Induced Criticality of Collective Excitation in a Trapped Bose-Einstein Condensate

TL;DR

This paper studies how anharmonic trapping potentials and interatomic forces influence low-energy excitations in Bose-Einstein condensates, revealing critical points where stability is lost or excitation frequencies are altered.

Contribution

It derives the dispersion relations for surface and compression modes in anharmonic traps, identifying critical values affecting condensate stability and excitation behavior.

Findings

Two excitation branches with critical values identified.

Anharmonicity can destabilize the condensate at upper limits.

Collective excitation frequencies can be lower due to anharmonic effects.

Abstract

We investigate the low energy excitations of a dilute atomic Bose gas confined in a anharmonic trap interacting with repulsive forces. The dispersion law of both surface and compression modes are derived and analyzed for large numbers of atoms in the trap, which show two branches of excitation and appear a two critical value. For a upper limit, BEC can be unstable with respect to some specific collective excitation, while for the lower limit, the frequency of collective excitation under anharmonic influence can be effectively lower than that without anharmonicity. Our work reveals the key role played by the anharmonicity and interatomic forces which introduce a rich structure in the dynamic behavior of these new many-body systems.