Periodically dressed Bose-Einstein condensate: a superfluid with an anisotropic and variable critical velocity.
We consider a two-component atomic gas illumined by two intersecting laser beams which induce Raman coupling between the components. This spatially periodic coupling modifies the dispersion relation of the gas. Properties of a Bose-Einstein condensate of such a gas are strongly affected by this modification. Using the quasiparticle excitation spectrum derived from a Bogoliubov transformation, the Landau critical velocity is found to be anisotropic and can be widely tuned by varying properties of the dressing laser beams.
Higbie
J
J
Department of Physics, University of California, Berkeley, California 94720, USA.
Stamper-Kurn
D M
DM