Coherent ratchets in driven Bose-Einstein condensates

TL;DR

This paper investigates how a Bose-Einstein condensate responds to periodic driving, demonstrating the conditions under which a coherent quantum ratchet effect can be induced through symmetry control.

Contribution

It reveals how space and time symmetry breaking in driven BECs can generate directed currents, highlighting the role of interactions and chaos in the ratchet mechanism.

Findings

Weak driving leads to regular, interaction-governed behavior.

Breaking both space and time symmetries induces directed current.

Strong driving causes chaotic dynamics and effective irreversibility.

Abstract

We study the response of a Bose-Einstein condensate to an unbiased periodic driving potential. By controlling the space and time symmetries of the driving we show how a directed current can be induced, producing a coherent quantum ratchet. Weak driving induces a regular behavior that is strongly governed by the interparticle interaction. Breaking both space and time symmetries is required to produce current flow. For strong driving the behavior becomes chaotic. The resulting effective irreversibility renders the space asymmetry sufficient to produce the ratchet effect, although the system is completely coherent.