Oscillating Superfluidity of Bosons in Optical Lattices

Following a suggestion by Orzel et al. [Science 291, 2386 (2001)], we analyze bosons in an optical lattice undergoing a sudden parameter change from the Mott to superfluid phase. We introduce a modified coherent states path integral to describe both phases. The saddle point theory yields collective oscillations of the uniform superfluid order parameter. We calculate its damping rate by phason pair emission. In two dimensions the overdamped region largely overlaps with the quantum critical region. Measurements of critical dynamics on the Mott side are proposed.

Figure 1

Oscillations of the superfluid OP $\Psi$ in a system prepared in the Mott state. (a) Mean field energy, where the equilibrium ground state is marked by point (2). (b) Solutions of the saddle point Eq. (18), which exhibits macroscopic oscillations. The dashed line indicates the superfluid OP in the ground state (2).