Quantum resonances and rectification of driven cold atoms in optical lattices

TL;DR

This paper investigates how quantum resonances influence current rectification in driven cold atoms within optical lattices, revealing tunable quantum effects that enhance control over atomic transport.

Contribution

It demonstrates the role of Floquet eigenstate desymmetrization and quantum resonances in controlling current in quantum ratchets, with tunable parameters for experimental setups.

Findings

Quantum resonances cause resonant changes in current.

Floquet eigenstates become transporting due to desymmetrization.

Resonance features are tunable via experimental parameters.

Abstract

Classical Hamiltonian ratchets have been recently successfully realized using cold atoms in driven optical lattices. Here we study the current rectification of the motion of a quantum particle in a periodic potential exposed to an external ac field. The dc current appears due to the desymmetrization of Floquet eigenstates, which become transporting. Quantum dynamics enhances the dependence of the current on the initial phase of the driving field. By changing the laser field parameters which control the degree of space-time asymmetry, Floquet eigenstates are tuned through avoided crossings. These quantum resonances induce resonant changes of the resulting current. The width, strength and position of these quantum resonances are tunable using control parameters of the experimental realization with cold atoms.