Thermopower-Based Hot Electron Thermometry of Helium Surface States at 1.6 K

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.