Multi-band quantum ratchets

TL;DR

This paper models multi-band quantum ratchets using a tight-binding approach, deriving a current formula and predicting rectification and current reversals in vortex quantum ratchet devices.

Contribution

It introduces a novel multi-band theoretical framework for quantum ratchets, including a closed-form current expression and analysis of rectification effects.

Findings

No current rectification in single-band ratchets.

Current reversals occur with changes in ac-field amplitude or frequency.

Application to vortex quantum ratchets predicts rectification phenomena.

Abstract

We investigate directed motion in non-adiabatically rocked ratchet systems sustaining few bands below the barrier. Upon restricting the dynamics to the lowest M bands, the total system-plus-bath Hamiltonian is mapped onto a discrete tight-binding model containing all the information both on the intra- and inter-well tunneling motion. A closed form for the current in the incoherent tunneling regime is obtained. In effective single-band ratchets, no current rectification occurs. We apply our theory to describe rectification effects in vortex quantum ratchets devices. Current reversals upon variation of the ac-field amplitude or frequency are predicted.