Voltage rectification by a SQUID ratchet

TL;DR

This paper demonstrates that an asymmetric dc SQUID can function as a voltage ratchet, producing a fixed voltage direction under alternating current due to phase dynamics influenced by magnetic flux.

Contribution

It introduces the concept of a SQUID acting as a ratchet device, revealing how phase asymmetry and magnetic flux lead to voltage rectification.

Findings

Existence of a parameter range with fixed voltage sign

Voltage rectification independent of external current direction

Identification of conditions for fixed average voltage

Abstract

We argue that the phase across an asymmetric dc SQUID threaded by a magnetic flux can experience an effective ratchet (periodic and asymmetric) potential. Under an external ac current, a rocking ratchet mechanism operates whereby one sign of the time derivative of the phase is favored. We show that there exists a range of parameters in which a fixed sign (and, in a narrower range, even a fixed value) of the average voltage across the ring occurs, regardless of the sign of the external current dc component.