Pairing and persistent currents - the role of the far levels

TL;DR

This paper investigates how pairing interactions influence the orbital magnetic response of disordered metallic rings, highlighting the significance of high energy level occupations in the many-body ground state.

Contribution

It provides a first-order expansion of the reduced BCS model to connect magnetic response with high energy level occupations in disordered rings.

Findings

Large magnetic response linked to high energy level occupations

First-order expansion of the reduced BCS model used

Connection between pairing and orbital magnetic response

Abstract

We calculate the orbital magnetic response to Aharonov Bohm flux of disordered metallic rings with attractive pairing interaction. We consider the reduced BCS model, and obtain the result as an expansion of its exact solution to first order in the interaction. We emphasize the connection between the large magnetic response and the finite occupation of high energy levels in the many-body ground state of the ring.