Decoherence of Cooper pairs and subgap magnetoconductance of superconducting hybrids

TL;DR

This paper investigates how electron-electron interactions limit superconducting correlations in diffusive normal metals and affect subgap magnetoconductance in superconductor-normal metal hybrids, revealing two key magnetic field effects.

Contribution

It demonstrates the fundamental restriction of superconducting correlation penetration due to electron-electron interactions and analyzes their impact on subgap magnetoconductance in SN hybrids.

Findings

Electron-electron interactions restrict superconducting correlation penetration.

Magnetic field causes temperature-independent dephasing of Cooper pairs.

Zeeman splitting influences subgap magnetoconductance.

Abstract

We demonstrate that electron-electron interactions fundamentally restrict the penetration length of superconducting correlations into a diffusive normal metal (N) attached to a superconductor (S). We evaluate the subgap magnetoconductance $G$ of SN hybrids in the presence of electron-electron interactions and demonstrate that the effect of the magnetic field on $G$ is twofold: It includes ($i$) additional temperature independent dephasing of Cooper pairs and ($ii$) Zeeman splitting between the states with opposite spins. The dephasing length of Cooper pairs can be directly extracted from measurements of the subgap magnetoconductance in SN systems at low temperatures.