A Direct Determination of the Temperature of Overheated Electrons in an Insulator

TL;DR

This paper introduces a novel measurement technique using AC-DC crossed measurements to directly determine the electron temperature in disordered superconductors, confirming overheating as the cause of nonlinear current-voltage behavior.

Contribution

It presents a new experimental method to accurately measure electron overheating, providing strong evidence for overheating as the origin of discontinuous I-V characteristics in disordered superconductors.

Findings

Electron temperature matches in transverse and longitudinal measurements.

Discontinuous I-V characteristics are explained by electron overheating.

Method can be applied to other systems with nonlinear I-V behavior.

Abstract

Highly disordered superconductors, in the magnetic-field-driven insulating state, can show discontinuous current-voltage characteristics. Electron overheating has been shown to give a consistent description of this behavior, but there are other, more exotic, explanations including a novel, superinsulating state and a many-body localized state. We present AC-DC crossed-measurements, in which the application of a DC voltage is applied along our sample, while a small AC voltage is applied in the transverse direction. We varied the DC voltage and observed a simultaneous discontinuity in both AC and DC currents. We show that the inferred electron-temperature in the transverse measurement matches that in the longitudinal one, strongly supporting electron overheating as the source of observed current-voltage characteristics. Our measurement technique may be applicable as a method of probing electron overheating in many other physical systems, which show discontinuous or non-linear current-voltage characteristics.