Transport properties of overheated electrons trapped on a Helium surface

TL;DR

This paper provides a theoretical analysis of the transport properties of overheated electrons trapped on a Helium surface, predicting how photocurrent behavior depends on electron temperature and confinement, and introduces new methods for solving related equations.

Contribution

It offers a quantitative model of photocurrent dependence on electron temperature and confinement, and develops numerical and analytical methods for low-temperature Poisson-Boltzmann equations.

Findings

Photocurrent can reverse sign depending on confinement parameters.

Overheating significantly affects electron transport properties.

New methods for solving Poisson-Boltzmann equations at low temperatures.

Abstract

An ultra-strong photovoltaic effect has recently been reported for electrons trapped on a liquid Helium surface under a microwave excitation tuned at intersubband resonance [D. Konstantinov et. al. : J. Phys. Soc. Jpn. 81, 093601 (2012) ]. In this article, we analyze theoretically the redistribution of the electron density induced by an overheating of the surface electrons under irradiation, and obtain quantitative predictions for the photocurrent dependence on the effective electron temperature and confinement voltages. We show that the photo-current can change sign as a function of the parameters of the electrostatic confinement potential on the surface, while the photocurrent measurements reported so far have been performed only at a fixed confinement potential. The experimental observation of this sign reversal could provide a reliable estimation of the electron effective temperature in this new out of equilibrium state. Finally, we have also considered the effect of the temperature on the outcome of capacitive transport measurement techniques. These investigations led us to develop, numerical and analytical methods for solving the Poisson-Boltzmann equation in the limit of very low temperatures which could be useful for other systems.