Propagation of Sound in a Bose-Einstein Condensate

TLDR

Sound propagation has been investigated in magnetically trapped dilute Bose‑Einstein condensates. Localized excitations were created by abruptly changing the trapping potential with a focused laser beam, and the resulting sound propagation was tracked via rapid, nondestructive phase‑contrast imaging. The measured sound speed varied with density in agreement with Bogoliubov theory, and the technique could be applied to detect high‑lying modes and possibly second sound.

Abstract

Sound propagation has been studied in a magnetically trapped dilute Bose-Einstein condensate. Localized excitations were induced by suddenly modifying the trapping potential using the optical dipole force of a focused laser beam. The resulting propagation of sound was observed using a novel technique, rapid sequencing of nondestructive phase-contrast images. The speed of sound was determined as a function of density and found to be consistent with Bogoliubov theory. This method may generally be used to observe high-lying modes and perhaps second sound.