Finite quasiparticle lifetime in disordered superconductors

TL;DR

This study demonstrates that the Mattis-Bardeen model with a finite quasiparticle lifetime accurately describes the complex conductivity of highly disordered superconducting MoC films, with scattering effects significantly reducing quasiparticle lifetime.

Contribution

It provides experimental validation of the Mattis-Bardeen model with finite quasiparticle lifetime in disordered superconductors, linking scattering effects to quasiparticle dynamics.

Findings

The Mattis-Bardeen model fits the experimental data well.

Quasiparticle lifetime is reduced by scattering effects.

Scanning tunneling spectroscopy confirms scattering characteristics.

Abstract

We investigate the complex conductivity of a highly disordered MoC superconducting film with $k_Fl\approx 1$, where $k_F$ is the Fermi wavenumber and $l$ is the mean free path, derived from experimental transmission characteristics of coplanar waveguide resonators in a wide temperature range below the superconducting transition temperature $T_c$. We find that the original Mattis-Bardeen model with a finite quasiparticle lifetime, $\tau$, offers a perfect description of the experimentally observed complex conductivity. We show that $\tau$ is appreciably reduced by scattering effects. Characteristics of the scattering centers are independently found by the scanning tunneling spectroscopy and agree with those determined from the complex conductivity.