Direct observation of non-local effects in a superconductor

TL;DR

This study provides the first direct, model-independent evidence of non-local electromagnetic response in a superconductor by measuring the local magnetic field profile beneath a lead film's surface.

Contribution

It demonstrates the use of low energy muon spin rotation to directly observe non-local effects in a superconductor, a novel experimental validation.

Findings

B(z) deviates from exponential decay

First direct proof of non-local response in a superconductor

Measurement technique confirms theoretical predictions

Abstract

We have used the technique of low energy muon spin rotation to measure the local magnetic field profile B(z) beneath the surface of a lead film maintained in the Meissner state (z depth from the surface, z <= 200 nm). The data unambiguously show that B(z) clearly deviates from an exponential law and represent the first direct, model independent proof for a non-local response in a superconductor.