Bogoliubov speed of sound for a dilute Bose-Einstein condensate in a 3d optical latticeD. Boers, C. Weiss and M. Holthaus
Institut für Physik, Carl von Ossietzky Universität - D-26111 Oldenburg, Germany
(Received 12 May 2004; accepted in final form 8 July 2004)
We point out that the velocity of propagation of sound wavepackets in a Bose-Einstein condensate filling a three-dimensional cubic optical lattice undergoes a maximum with increasing lattice depth. For a realistic choice of parameters, the maximum sound velocity in a lattice condensate can exceed the sound velocity in a homogeneous condensate with the same average density by 30%. The maximum falls into the superfluid regime, and should be observable under currently achievable laboratory conditions.
03.75.Lm - Tunneling, Josephson effect, Bose-Einstein condensates in periodic potentials, solitons, vortices and topological excitations.
03.75.Kk - Dynamic properties of condensates; collective and hydrodynamic excitations, superfluid flow.
05.30.Jp - Boson systems.
© EDP Sciences 2004