Mott insulator dynamics

TL;DR

This paper investigates the dynamics of Mott insulators in a lattice Bose gas under time-dependent potentials, revealing conditions for melting and the effects of rapid potential changes and stirring on the insulating state.

Contribution

It provides a mean-field analysis of Mott insulator response to dynamic external potentials, identifying key factors that prevent or induce melting.

Findings

Mott insulators remain insulating under abrupt potential switches due to Bloch oscillations.

A stirrer affects the Mott insulator only if it starts in a superfluid region and moves at a tunneling-scale velocity.

Slow or smooth potential changes can allow the Mott insulator to adjust and melt.

Abstract

The hydrodynamics of a lattice Bose gas in a time-dependent external potential is studied in a mean-field approximation. The conditions under which a Mott insulating region can melt, and the local density adjust to the new potential, are determined. In the case of a suddenly switched potential, it is found that the Mott insulator stays insulating and the density will not adjust if the switch is too abrupt. This comes about because too rapid currents result in Bloch oscillation-type current reversals. For a stirrer moved through a Mott insulating cloud, it is seen that only if the stirrer starts in a superfluid region and the velocity is comparable to the time scale set by the tunneling, will the Mott insulator be affected.