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 nonlinear mobility. We demonstrate the use of this method by measuring the heating of SSE at 1.6 K in a microchannel device with 0.6  μm 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.