Local thermometry of NbSe$_2$ flake with delta-$T$ noise measurements

TL;DR

This paper uses delta-T noise measurements to study local temperature variations and electron-phonon interactions in NbSe$_2$ flakes, revealing insights into superconducting and normal states.

Contribution

It introduces a novel delta-T noise measurement technique to probe local thermometry and electron-phonon scattering in NbSe$_2$ superconductors.

Findings

Effective charge doubling in shot noise indicating Andreev reflection

Extraction of electron-phonon scattering length and its temperature dependence

Qualitative agreement of delta-T noise in superconducting state with theoretical expectations

Abstract

We perform transport and noise measurements for device consisting of a thin NbSe$_2$ flake laid onto the predefined gold electrodes and covered with a thin hBN flake. In the shot noise of a NbSe$_2$/Au tunnel junction (TJ), we identify Andreev reflection regime by demonstrating the effective charge doubling. Further, by creating temperature gradient across the TJ and measuring its delta-$T$ noise in the normal state, we extract electron-phonon scattering length in NbSe$_2$ and its $T$-dependence. The results of delta-$T$ noise measurements in the absence of a magnetic field when the flake is superconducting are in qualitative agreement with expectations. The introduced approach is promising for the study of nonequilibrium configurations in superconductors.