Direct current in a stirred optical lattice

TL;DR

This paper investigates how circular stirring of an optical lattice can induce a transient direct current in bosonic atoms, revealing insights into non-equilibrium dynamics and transport in driven quantum systems.

Contribution

It demonstrates how lattice symmetry breaking and periodic stirring can generate a nonzero group velocity and transient current in bosonic atoms, extending understanding of driven optical lattices.

Findings

Circular stirring induces a nonzero group velocity at the Brillouin zone center.

The induced current is transient when the drive frequency avoids resonant absorption.

Experimental relaxation studies can shed light on equilibration in driven quantum systems.

Abstract

We study how the energy dispersion of bosonic atoms loaded into an optical lattice becomes modified due to periodic circular stirring of the lattice to the second order in the strength of stirring. If the lattice breaks mirror symmetry, the bosonic atoms may acquire a nonzero group velocity at the center of the Brillouin zone and produce a nonzero direct current. This effect is similar to the circular photogalvanic effect in solid-state physics. It can be used to transport neutral bosonic atoms in an optical lattice over a given distance in an arbitrary direction. However, when the drive frequency is detuned to avoid resonant transitions with energy absorption, we argue that the induced current is not persistent, but transient. An experimental study of the induced current relaxation could give answers to perplexing questions about equilibrization in driven systems.