Far-Infrared Conductivity Measurements of Pair Breaking in Superconducting Nb$_{0.5}$Ti$_{0.5}$N Thin Films Induced by an External Magnetic Field

TL;DR

This study measures the complex optical conductivity of Nb$_{0.5}$Ti$_{0.5}$N thin films under magnetic fields, confirming the pair-breaking theory's predictions for superconducting gap suppression.

Contribution

First direct optical measurement of pair-breaking effects in Nb$_{0.5}$Ti$_{0.5}$N thin films under magnetic fields, validating Abrikosov-Gor'kov theory.

Findings

Superconducting gap decreases with increasing magnetic field.

Optical conductivity results agree with pair-breaking theory.

Confirmed theoretical predictions for optical properties under magnetic fields.

Abstract

We report the complex optical conductivity of a superconducting thin-film of Nb$_{0.5}$Ti$_{0.5}$N in an external magnetic field. The field was applied parallel to the film surface and the conductivity extracted from far-infrared transmission and reflection measurements. The real part shows the superconducting gap, which we observe to be suppressed by the applied magnetic field. We compare our results with the pair-breaking theory of Abrikosov and Gor'kov and confirm directly the theory's validity for the optical conductivity.