Thermopower-based hot electron thermometry of helium surface states at 1.6 K

TL;DR

This paper introduces a novel thermometry method based on thermopower to measure the temperature of surface state electrons on superfluid helium-4, avoiding complex mobility knowledge and providing reliable temperature measurements at 1.6 K.

Contribution

The authors develop and demonstrate a thermopower-based technique for electron temperature measurement that simplifies the process compared to previous methods.

Findings

The method accurately measures electron energy relaxation at 1.6 K.

It distinguishes contributions from vapor atom and 2-ripplon scattering.

The technique offers a reliable and less complex alternative for electron thermometry.

Abstract

We have developed a method to probe the temperature of surface state electrons (SSE) above a superfluid Helium-4 surface using the Seebeck effect. In contrast to previously used SSE thermometry, this technique does not require detailed knowledge of the non-linear mobility. We demonstrate the use of this method by measuring energy relaxation of SSE at 1.6 K in a microchannel device with $0.6\:\mu\mbox{m}$ deep helium. In this regime, both vapor atom scattering and 2-ripplon scattering contribute to energy relaxation to which we compare our measurements. We conclude that this technique provides a reliable measure of electron temperature while requiring a less detailed understanding of the electron interactions with the environment than previously utilized thermometry techniques.