758 research outputs found
Unusual behavior of sound velocity of a Bose gas in an optical superlattice at quasi-one-dimension
A Bose gas trapped in a one-dimensional optical superlattice has emerged as a
novel superfluid characterized by tunable lattice topologies and tailored band
structures. In this work, we focus on the propagation of sound in such a novel
system and have found new features on sound velocity, which arises from the
interplay between the two lattices with different periodicity and is not
present in the case of a condensate in a monochromatic optical lattice.
Particularly, this is the first time that the sound velocity is found to first
increase and then decrease as the superlattice strength increases even at one
dimension. Such unusual behavior can be analytically understood in terms of the
competition between the decreasing compressibility and the increasing effective
mass due to the increasing superlattice strength. This result suggests a new
route to engineer the sound velocity by manipulating the superlattice's
parameters. All the calculations based on the mean-field theory are justified
by checking the exponent of the off-diagonal one-body density matrix
that is much smaller than 1. Finally, the conditions for possible experimental
realization of our scenario are also discussed.Comment: 10 pages, 5 figure
- …