Effect of pair-breaking on mesoscopic persistent currents well above the superconducting transition temperature

TL;DR

This paper investigates how pair-breaking affects mesoscopic persistent currents in low-temperature superconductors, revealing that currents remain robust even when the transition temperature is suppressed to zero.

Contribution

It demonstrates that persistent currents are largely unaffected by pair-breaking in a broad parameter range, offering insights into noble metals' properties and methods to estimate their intrinsic transition temperatures.

Findings

Persistent currents remain strong despite suppressed transition temperature.

Transition temperature can be renormalized to zero without significantly affecting currents.

Provides a potential explanation for observed currents in noble metals.

Abstract

We consider the mesoscopic normal persistent current (PC) in a very low-temperature superconductor with a bare transition temperature $T_c^0$ much smaller than the Thouless energy $E_c$. We show that in a rather broad range of pair-breaking strength, $T_c^0 \lesssim \hbar/\tau_s \lesssim E_c$, the transition temperature is renormalized to zero, but the PC is hardly affected. This may provide an explanation for the magnitude of the average PC's in the noble metals, as well as a way to determine their $T_c^0$'s.