Origin of Spontaneous Currents in a Superconductor-Ferromagnet Proximity System

TL;DR

This paper investigates the quantum origin of spontaneous currents in superconductor-ferromagnet heterostructures, showing they are a true ground state effect caused by Andreev bound states, affecting the system's total energy.

Contribution

It provides a detailed analysis of the energy contributions and confirms that spontaneous currents are a fundamental quantum ground state phenomenon in these systems.

Findings

Spontaneous currents are caused by Andreev bound states.

Currents can be fully spin-polarized.

Current presence affects total energy contributions.

Abstract

We have previously shown that a ferromagnet-superconductor heterostructure may possess a spontaneous current circulation parallel to the interface. This current is caused by Andreev bound states in the thin ferromagnetic layer, and can be fully spin-polarized. Here we investigate the total energy of the system in cases where the current either does or does not flow. We show that the current is a true quantum ground state effect, and examine the effect of the current on the different contributions to the total energy.