Collective oscillations in two-dimensional Bose-Einstein condensate

TL;DR

This paper investigates how the reduced two-dimensional geometry of a pancake-shaped Bose-Einstein condensate affects the frequencies of its collective oscillations, deriving analytical expressions across different scattering regimes.

Contribution

It introduces models for the coupling constant in various dimensional regimes and derives analytical formulas for monopole and quadrupole mode frequencies using sum rule approach.

Findings

Monopole mode frequencies are significantly affected by dimensional reduction.

Frequencies evolve as the system transitions between scattering regimes.

Analytical expressions match numerical results across regimes.

Abstract

We study the effect of lower dimensional geometry on the frequencies of the collective oscillations of a Bose-Einstein condensate confined in a trap. To study the effect of two dimensional geometry we consider a pancake-shaped condensate confined in a harmonic trap and employ various models for the coupling constant depending on the thickness of the condensate relative to the the value of the scattering length. These models correspond to different scattering regimes ranging from quasi-three dimensional to strictly two dimensional regimes. Using these models for the coupling parameter and sum rule approach of the many-body response theory we derive analytical expressions for the frequencies of the monopole and the quadrupole modes. We show that the frequencies of monopole mode of the collective oscillations are significantly altered by the reduced dimensionality and also study the evolution of the frequencies as the system make transition from one regime to another.