Controlling the Momentum Current of an Off-resonant Ratchet

TL;DR

This paper experimentally demonstrates control over the direction of a quantum ratchet current in a Bose-Einstein Condensate using a universal scaling law, confirming theoretical predictions about symmetry-independent control.

Contribution

It provides the first experimental verification that ratchet current direction can be controlled without symmetry breaking, using a single parameter scaling law.

Findings

Ratchet current direction is controllable via experimental parameters.

A universal scaling law describes the ratchet current behavior.

Experimental results confirm theoretical predictions.

Abstract

We experimentally investigate the phenomenon of a quantum ratchet created by exposing a Bose-Einstein Condensate to short pulses of a potential which is periodic in both space and time. Such a ratchet is manifested by a directed current of particles, even though there is an absence of a net bias force. We confirm a recent theoretical prediction [M. Sadgrove and S. Wimberger, New J. Phys. \textbf{11}, 083027 (2009)] that the current direction can be controlled by experimental parameters which leave the underlying symmetries of the system unchanged. We demonstrate that this behavior can be understood using a single variable containing many of the experimental parameters and thus the ratchet current is describable using a single universal scaling law.