Winding branes and persistent currents

TL;DR

This paper models persistent currents in superconducting rings using winding D5 branes around D3 branes, analyzing the stability and decay mechanisms of the superconducting state in a holographic framework.

Contribution

It introduces a holographic model of superconducting rings with winding branes, exploring the existence, stability, and decay of gapped superconducting states at large N.

Findings

Gapped classical solutions exist for any winding number density q.

States become unstable when q exceeds a critical value q_m.

Decay involves string production via a Hanany-Witten effect.

Abstract

A D5 brane winding around a stack of D3 branes can be used as a model of persistent current in a thin superconducting ring, with the number N of D3s corresponding to the number of transverse channels in the ring. We consider, in the large N limit, existence and properties of a gapped superconducting state with a uniform winding number density q. We find that there is a gapped classical solution for any q, no matter how large, but when q is larger than a certain q_m the state is unstable with respect to decay by phase slips. We argue that this decay produces strings via a version of the Hanany-Witten effect (in a non-transverse, non-supersymmetric arrangement of branes). This parallels the requirement of quasiparticle production in a clean (disorder-free) wire in field theory of superconductivity.