# Superconducting fluctuations in a thin NbN film probed by the Hall effect

## TL;DR

This study investigates how superconducting fluctuations in a thin NbN film influence its conductivity and Hall effect near the transition, confirming Gaussian fluctuation theory with quantitative agreement.

## Contribution

It provides the first detailed experimental validation of Gaussian fluctuation theory for the conductivity tensor in a superconducting film near the transition.

## Key findings

- Superconducting fluctuations cause a sign change in the Hall coefficient.
- Scaling behaviors match Gaussian fluctuation theory predictions.
- Quantitative agreement achieved without adjustable parameters.

## Abstract

We present a comprehensive study of how superconducting fluctuations in the normal state contribute to the conductivity tensor in a thin (119 $\AA$) 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 behaviours 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 is 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.