Paramagnetic instability at normal-metal - superconductor interfaces

TL;DR

This paper investigates how electron interactions in a normal metal in contact with a superconductor lead to paramagnetic currents and enhanced local density of states, explaining phenomena like paramagnetic reentrance.

Contribution

It introduces a model accounting for repulsive interactions in the normal metal, revealing the origin of paramagnetic instability at NS interfaces.

Findings

Enhanced local density of states near the interface

Spontaneous paramagnetic interface currents

Orbital magnetic moments showing paramagnetic reentrance features

Abstract

We study the proximity coherence in a mesoscopic normal-metal film (N) in contact with a superconductor (S). Accounting for a repulsive interaction between the electrons in the normal metal, we find an enhanced local density of states close to the NS interface. The sharp peak in the density is pinned to the Fermi energy and leads to spontaneous paramagnetic interface currents. The induced orbital magnetic moments exhibit the characteristic features of paramagnetic reentrance observed in normal-metal coated superconducting cylinders [Phys. Rev. Lett. 65, 1514 (1990)].