Resistivity anomalies and intrinsic spin-orbit coupling in superconducting thin film solid solutions of Nb$_{1-x}$U$_x$ for $0.15 < x < 0.40$

TL;DR

This study investigates how uranium doping affects the electrical resistivity, superconductivity, and spin-orbit coupling in Nb-U thin films, revealing complex interactions and spin relaxation mechanisms.

Contribution

It provides new insights into the relationship between uranium concentration, resistivity anomalies, and spin-orbit coupling in superconducting Nb-U thin films.

Findings

Superconductivity observed below 2 K in all samples.

Spin-orbit scattering scales with transport scattering, indicating Elliott-Yafet relaxation.

Magnetoresistivity suggests interplay between electron-electron interactions and localization.

Abstract

Polycrystalline thin films of $\mathrm{Nb}_{1-x}\mathrm{U}_{x}$ solid solutions with $0.15\leq x \leq 0.40$ were prepared via d.c. magnetron sputtering at ambient conditions. X-ray characterisation of the samples revealed a systematic shift of the (110) Nb Bragg reflection with U concentration, consistent with substitutional replacement of the Nb by U. Superconductivity was observed in all samples below $2$ K. Analysis of the superconducting critical fields revealed a direct scaling of the spin-orbit scattering and transport scattering times, indicating Elliott-Yafet-type spin relaxation in the system. Magnetoresistivity measurements showed a feature in the range $4$ K $\leq T \leq30$ K suggesting a possible a complex interplay between electron-electron interaction and localisation physics.