Quasi one-dimensional Bose-Einstein condensate in gravito-optical surface trap

TL;DR

This paper investigates the static and dynamic behavior of a quasi-one-dimensional Bose-Einstein condensate in a gravito-optical surface trap, combining analytical and numerical methods to understand its expansion and interference patterns.

Contribution

It provides approximate analytical solutions for the BEC in the trap and compares them with numerical results, enhancing understanding of BEC dynamics in gravito-optical traps.

Findings

Non-ballistic expansion of BEC after trap release

Observation of self-interference patterns for large atom numbers

Revival of wave packet with interference for small atom numbers

Abstract

We study both static and dynamic properties of a weakly interacting Bose-Einstein condensate (BEC) in a quasi one-dimensional gravito-optical surface trap, where the downward pull of gravity is compensated by the exponentially decaying potential of an evanescent wave. First, we work out approximate solutions of the Gross-Pitaevskii equation for both a small number of atoms using a Gaussian ansatz and a larger number of atoms using the Thomas-Fermi limit. Then we confirm the accuracy of these analytical solutions by comparing them to numerical results. From there, we numerically analyze how the BEC cloud expands non-ballistically, when the confining evanescent laser beam is shut off, showing agreement between our theoretical and previous experimental results. Furthermore, we analyze how the BEC cloud expands non-ballistically due to gravity after switching off the evanescent laser field in the presence of a hard-wall mirror. There we find that the BEC shows significant self-interference patterns for a large number of atoms, whereas for a small number of atoms, a revival of the BEC wave packet with few matter-wave interference patterns is observed.