Suppression of Faraday waves in a Bose-Einstein condensate in the presence of an optical lattice

TL;DR

This paper investigates how a one-dimensional optical lattice influences the formation of Faraday waves in a Bose-Einstein condensate, revealing conditions under which these waves are suppressed due to dynamical instability.

Contribution

It demonstrates the suppression mechanism of Faraday waves in a BEC caused by increased optical lattice depth and the resulting dynamical instability.

Findings

Faraday waves form in shallow optical lattices with propagating phonons.

Increasing lattice depth decreases local sound velocity.

At a critical depth, Faraday wave formation is suppressed due to instability.

Abstract

We study the formation of Faraday waves in an elongated Bose-Einstein condensate in presence of a one-dimensional optical lattice, where phonons are parametrically excited by modulating the radial confinement of the condensate. For very shallow optical lattices, phonons with a well-defined wave vector propagate along the condensate, as in the absence of the lattice, and we observe the formation of a Faraday pattern. By increasing the potential depth, the local sound velocity decreases and when it equals the condensate local phase velocity, the condensate becomes dynamically unstable and the parametric excitation of Faraday waves is suppressed.