We present a comprehensive study of how superconducting fluctuations in the normal state contribute to the conductivity tensor in a thin (119 Å) film of NbN. It is shown how these fluctuations drive a sign change in the Hall coefficient $R_{\mathrm{H}}$ for low magnetic fields near the superconducting transition. The scaling behaviors as a function of distance to the transition $\epsilon =ln(T/T_{\mathrm{c}})$ of the longitudinal (${\sigma }_{\mathrm{xx}}$) and transverse (${\sigma }_{\mathrm{xy}}$) conductivity are found to be consistent with Gaussian fluctuation theory. Moreover, excellent quantitative agreement between theory and experiment is obtained without any adjustable parameters. Our experimental results thus provide a case study of the conductivity tensor originating from short-lived Cooper pairs.

• Received 14 December 2016

DOI:https://doi.org/10.1103/PhysRevB.95.224501

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

Published by the American Physical Society