Energy relaxation in graphene and its measurement with supercurrent

TL;DR

This paper investigates inelastic energy relaxation in graphene by measuring the critical Josephson current in graphene-superconductor devices, revealing electron-electron interactions as the dominant relaxation process with faster scattering times than theoretical predictions.

Contribution

It introduces a method to probe inelastic scattering in graphene using supercurrent measurements, highlighting the dominance of electron-electron interactions over phonons.

Findings

Electron-electron scattering time is 5-13 ps at 500 mK.

The measured scattering time is 1-2 orders of magnitude smaller than theoretical predictions.

Critical Josephson current effectively probes energy relaxation processes.

Abstract

We study inelastic energy relaxation in graphene for low energies to find out how electrons scatter with acoustic phonons and other electrons. By coupling the graphene to superconductors, we create a strong dependence of the measured signal, i.e.,\ critical Josephson current, on the electron population on different energy states. Since the relative population of high- and low-energy states is determined by the inelastic scattering processes, the critical current becomes an effective probe for their strength. We argue that the electron-electron interaction is the dominant relaxation method and, in our model of two-dimensional electron-electron scattering, we find a scattering time $\tau_{e-e}=5... 13$ ps at T=500 mK, 1-2 orders of magnitude smaller than predicted by theory.