Reversible ratchet effects in a narrow superconducting ring

TL;DR

This paper investigates the ratchet effect in a pinning-free superconducting ring, revealing a novel signal reversal at high magnetic fields and demonstrating potential for superconducting diode applications.

Contribution

It introduces the first observation of ratchet signal reversal in a pinning-free superconducting ring using TDGL equations, highlighting asymmetric flux barriers as the cause.

Findings

Ratchet signal reversal occurs at high magnetic fields.

The effect exceeds that of asymmetric pinning potentials.

Feasibility of superconducting diode effect in mesoscopic superconductors.

Abstract

We study the ratchet effect in a narrow pinning-free superconductive ring based on time-dependent Ginzburg-Landau (TDGL) equations. Voltage responses to external dc an ac currents at various magnetic fields are studied. Due to asymmetric barriers for flux penetration and flux exit in the ring-shaped superconductor, the critical current above which the flux-flow state is reached, as well as the critical current for the transition to the normal state, are different for the two directions of applied current. These effects cooperatively cause ratchet signal reversal at high magnetic fields, which has not been reported to date in a pinning-free system. The ratchet signal found here is larger than those induced by asymmetric pinning potentials. Our results also demonstrate the feasibility of using mesoscopic superconductors to employ superconducting diode effect in versatile superconducting devices.