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

Inelastic scattering processes are crucial for understanding and describing a wide variety of phenomena observed in surface state electrons (SSE) on helium including non-linear transport and microwave absorption line shapes. Further interest in inelastic scattering has been motivated by the relevance to coherence times of Rydberg state based SSE qubits. Despite their fundamental importance, relatively little experimental work have examined inelastic processes which can be attributed to challenges associated with electron thermometry of hot SSE.

We have developed a method to probe SSE temperature using the Seebeck effect. We demonstrate the use of this technique by measuring SSE temperature as a function of applied power at a bath temperature of 1.6 K in a microchannel device with 0.6 μm deep helium. We compare our measurements to the predictions for both vapor atom and 2-ripplon scattering in the single electron regime. Our measurements demonstrate a strong qualitative agreement with the predictions and we attribute small quantitative discrepancies to many body effects. We conclude that this technique provides a reliable and flexible measure of electron temperature.