Pairing resonance as a normal-state spin probe in ultra-thin Al films

TL;DR

This paper introduces a method to analyze the pairing resonance in ultra-thin Al films at low temperatures and high magnetic fields, enabling extraction of key spin-related parameters from tunneling data.

Contribution

It provides an analytical framework for interpreting tunneling spectra in the normal state of ultra-thin superconducting films, allowing determination of spin parameters traditionally obtained in the superconducting phase.

Findings

Analytical expression for the tunneling density-of-states spectrum.

Extraction of spin-orbit scattering rate, Landau parameter G^0, and orbital pair-breaking parameter.

Method applicable at supercritical parallel magnetic fields.

Abstract

We present a quantitative analysis of the low-temperature, high parallel field pairing resonance in ultra-thin superconducting Al films with dimensionless conductance g>>1. In this regime we derive an analytical expression for the tunneling density-of-states spectrum from which a variety of normal-state spin parameters can be extracted. We show that by fitting tunneling data at several supercritical parallel magnetic fields we can determine all of the relevant parameters that have traditionally been obtained via fits to tunneling data in the superconducting phase. These include the spin-orbit scattering rate, the antisymmetric Landau parameter G^0, and the orbital pair-breaking parameter.