Determination of the Coherence Length and the Cooper-Pair Size in Unconventional Superconductors by Tunnelling Spectroscopy

TL;DR

This paper explores how tunnelling spectroscopy can be used to measure the coherence length and Cooper-pair size in unconventional superconductors by analyzing vortex core structures.

Contribution

It proposes a method to determine coherence length and Cooper-pair size in unconventional superconductors through tunnelling spectroscopy of vortex cores.

Findings

Method for estimating coherence length and Cooper-pair size

Analysis of vortex core structures in tunnelling spectra

Potential for experimental application in superconductor characterization

Abstract

The main purpose of the paper is to discuss a possibility of the determination of the values of the coherence length and the Cooper-pair size in unconventional superconductors by using tunnelling spectroscopy. In the mixed state of type-II superconductors, an applied magnetic field penetrates the superconductor in the form of vortices which form a regular lattice. In unconventional superconductors, the inner structure of a vortex core has a complex structure which is determined by the order parameter of the superconducting state and by the pairing wavefunction of the Cooper pairs. In clean superconductors, the spatial variations of the order parameter and the pairing wavefunction occur over the distances of the order of the coherence length and the Cooper-pair size, respectively. Therefore, by performing tunnelling spectroscopy along a line passing through a vortex core, one is able, in principle, to estimate the values of the coherent length and the Cooper-pair size.