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

摘要

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