Normal persistent currents in proximity-effect bilayers

TL;DR

This paper investigates how superconducting fluctuations influence persistent currents in bilayer rings with proximity effects, revealing that the persistent current decays more slowly than the transition temperature as the normal layer widens.

Contribution

It provides a detailed analysis of the proximity effect on persistent currents in bilayer systems, highlighting differences from magnetic impurity effects.

Findings

Persistent current decay is slower than transition temperature decay with increasing normal layer width.

Superconducting fluctuations contribute significantly to mesoscopic persistent currents.

Proximity effect results in pair-weakening rather than pair-breaking, affecting current behavior.

Abstract

We calculate the contribution of superconducting fluctuations to the mesoscopic persistent current of an ensemble of rings, each made of a superconducting layer in contact with a normal one, in the Cooper limit. The superconducting transition temperature of the bilayer decays very quickly with the increase of the relative width of the normal layer. In contrast, when the Thouless energy is larger than the temperature then the suppression of the persistent current with the increase of this relative width is much slower than that of the transition temperature. This effect is similar to that predicted for magnetic impurities, although the proximity effect considered here results in pair-weakening as opposed to pair-breaking.