Parametric excitation of a Bose-Einstein condensate in a 1D optical lattice

TL;DR

This paper investigates how periodic modulation of an optical lattice's depth induces parametric excitation in a Bose-Einstein condensate, leading to nonlinear dynamics and broadening of the condensate without significant depletion.

Contribution

It demonstrates the parametric excitation mechanism in BECs using Gross-Pitaevskii theory and reproduces experimental spectral features in the superfluid phase.

Findings

Parametric excitation occurs at half the modulation frequency.

Broadening of momentum distribution observed after modulation.

Results align with previous experimental measurements.

Abstract

We study the response of a Bose-Einstein condensate to a periodic modulation of the depth of an optical lattice. Using Gross-Pitaevskii theory, we show that a modulation at frequency Omega drives the parametric excitation of Bogoliubov modes with frequency Omega/2. The ensuing nonlinear dynamics leads to a rapid broadening of the momentum distribution and a consequent large increase of the condensate size after free expansion. We show that this process does not require the presence of a large condensate depletion. Our results reproduce the main features of the spectrum measured in the superfluid phase by Stoeferle et al., Phys. Rev. Lett. 92, 130403 (2004).