Fermi-liquid effects in the gapless state of marginally thin superconducting films

TL;DR

This study investigates the effects of Fermi-liquid interactions on the electronic density of states in thin aluminum superconducting films under high magnetic fields, revealing how quasiparticle interactions influence the transition to a gapless state.

Contribution

It provides the first experimental determination of the antisymmetric Fermi-liquid parameter G^0 in the gapless state of thin superconducting films, linking theory with tunneling spectroscopy data.

Findings

Measured and calculated tunneling spectra agree well.

Extracted the Fermi-liquid parameter G^0 and its quasiparticle density dependence.

Identified the role of Fermi-liquid effects in the gapless superconducting state.

Abstract

We present low temperature tunneling density-of-states measurements in Al films in high parallel magnetic fields. The thickness range of the films, t=6-9 nm, was chosen so that the orbital and Zeeman contributions to their parallel critical fields were comparable. In this quasi-spin paramagnetically limited configuration, the field produces a significant suppression of the gap, and at high fields the gapless state is reached. By comparing measured and calculated tunneling spectra we are able to extract the value of the antisymmetric Fermi-liquid parameter G^0 and thereby deduce the quasiparticle density dependence of the effective parameter G^0_{eff} across the gapless state.