Question

Is Bose-Einstein condensate in the optical lattice a single mode condensate?

Answer 1

Yes, There is a single condensate only. The additional peaks appear due to the small occupation of higher-energy states, as the increasing well depth encourages localization of particles.

Answer 2

Hey ^_^

There is a single condensate only. The additional peaks appear due to the small occupation of higher-energy states, as the increasing well depth encourages localization of particles....


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Looking at a condensate released from a lattice after a time of flight typically on the order of a few milliseconds amounts to observing its momentum distribution.
A harmonically trapped condensate has a Gaussian momentum distribution in the limit of small interactions, whereas in the Thomas-Fermi limit in which the interactions dominate over the kinetic energy contribution it has a parabolic density profile and expands self-similarly after being released. By contrast, a condensate in a periodic potential contains higher momentum contributions in multiples of 2 kL, their relative weights depending on the depth of the lattice. In fact, in the tight-binding limit see Sec. IV we can consider the condensate to be split up into an array of local wave functions that expand independently after the lattice has been switched off. Eventually they all overlap and form an interference pattern that in the absence of interactions is the Fourier transform of the initial condensate.

So yes,, it's a single condensate...