Oscillating Superfluidity of Bosons in Optical Lattices

TL;DR

This paper investigates the dynamic oscillations of superfluid order in bosons within optical lattices following a phase transition, providing theoretical predictions for observable interference patterns and damping behaviors.

Contribution

It introduces a modified coherent states path integral approach to analyze collective oscillations in the Bose Hubbard model during phase transitions.

Findings

Predicts collective oscillations of the superfluid order parameter.

Calculates damping rates due to phason pair emission.

Proposes experimental measurements of critical dynamics.

Abstract

We follow up on a recent suggestion by C. Orzel et. al., Science, 291, 2386 (2001), whereby bosons in an optical lattice would be subjected to a sudden parameter change from the Mott to the superfluid phase. We analyze the Bose Hubbard model with a modified coherent states path integral which can escribe - both - phases. The saddle point theory yields collective oscillations of the uniform superfluid order parameter. These would be seen in time resolved interference patterns made by the released gas. We calculate the collective oscillation's 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.