Pair-breaking effect on mesoscopic persistent currents

Abstract

We consider the contribution of superconducting fluctuations to the mesoscopic persistent current (PC) of an ensemble of normal metallic rings, made of a superconducting material whose low bare transition temperature $T_c^0$ is much smaller than the Thouless energy $E_c$. The effect of pair breaking is introduced via the example of magnetic impurities. We find that over a rather broad range of pair-breaking strength $\hslash /{\tau }_s$, such that $T_c^0\lesssim \hslash /{\tau }_s\lesssim E_c$, the superconducting transition temperature is normalized down to minute values or zero while the PC is hardly affected. This may provide an explanation for the magnitude of the average PC's in copper and gold, as well as a way to determine their $T_c^0$'s. The dependence of the current and the dominant superconducting fluctuations on $E_c{\tau }_s$ and on the ratio between $E_c$ and the temperature is analyzed. The measured PC's in copper (gold) correspond to $T_c^0$ of a few (a fraction of) mK.

References in corpus (2)

• Persistent currents in normal metal rings
• Fluctuation Superconductivity in Mesoscopic Aluminum Rings

Cited by in corpus (10)

• Fluctuation persistent current in small superconducting rings
• Persistent currents of noninteracting electrons
• Searching for thermal signatures of persistent currents in normal metal rings
• Limitations on the Ginzburg criterion for dirty superconductors
• Scale-dependent competing interactions: sign reversal of the average persistent current
• Superconducting fluctuations--Large Diamagnetism of Low $T_c$ Nanoparticles
• Normal persistent currents in proximity-effect bilayers
• Persistent Currents in Normal Metal Rings (Yale PhD thesis)
• Renormalization of competing interactions and superconductivity on small scales
• Fabrication and characterization of large arrays of mesoscopic gold rings on large-aspect-ratio cantilevers