Excitations of a Superfluid in a Three-Dimensional Optical Lattice

Christian Schori, Thilo Stöferle, Henning Moritz, Michael Köhl, Tilman Esslinger
2004 Physical Review Letters  
We prepare a Bose-Einstein condensed gas in a three-dimensional optical lattice and study the excitation spectrum of the superfluid phase for different interaction strengths. We probe the response of the system by modulating the depth of the optical lattice along one axis. The interactions can be controlled independently by varying the tunnel coupling along the other two lattice axes. In the weakly interacting regime we observe a small susceptibility of the superfluid to excitations, while for
more » ... tronger interactions an unexpected resonance appears in the excitation spectrum. In addition we measure the coherent fraction of the atomic gas, which determines the depletion of the condensate.
doi:10.1103/physrevlett.93.240402 pmid:15697784 fatcat:qyh5nq7lpbefrpd7o7gqj6d4fq