Parametric Excitation of a Bose-Einstein Condensate: From Faraday Waves to Granulation

TL;DR

This paper investigates how modulating interactions in an elongated Bose-Einstein condensate induces surface waves and granulation, revealing regimes explained by mean-field theory and beyond mean-field quantum fluctuations.

Contribution

It demonstrates the generation of Faraday waves and granulation in BECs through parametric excitation, combining experimental results with advanced theoretical models.

Findings

Resonant and parametric surface waves observed near specific modulation frequencies.

Granulated condensate characterized by quantum fluctuations, outside mean-field description.

Mean-field theory accurately predicts surface wave dispersion, beyond mean-field captures granulation phenomena.

Abstract

We explore, both experimentally and theoretically, the response of an elongated Bose-Einstein condensate to modulated interactions. We identify two distinct regimes differing in modulation frequency and modulation strength. Longitudinal surface waves are generated either resonantly or parametrically for modulation frequencies near the radial trap frequency or twice the trap frequency, respectively. The dispersion of these waves, the latter being a Faraday wave, is well-reproduced by a mean-field theory that accounts for the 3D nature of the elongated condensate. In contrast, in the regime of lower modulation frequencies we find that no clear resonances occur, but with increased modulation strength, the condensate forms an irregular granulated distribution that is outside the scope of a mean-field approach. We find that the granulated condensate is characterized by large quantum fluctuations and correlations, which are well-described with single-shot simulations obtained from wavefunctions computed by a beyond mean-field theory at zero temperature, the multiconfigurational time-dependent Hartree for bosons method.