Surface photocurrent in electron gas over liquid He subject to quantizing magnetic field

TL;DR

This paper investigates the photogalvanic effect in an electron gas over liquid helium under a quantizing magnetic field, revealing resonant behaviors and matching experimental data.

Contribution

It provides a theoretical analysis of the photogalvanic effect, including resonance phenomena and ripplon involvement, in a novel electron-helium system under magnetic fields.

Findings

Resonances occur at microwave frequencies near subband transition energies.

Additional resonances at multiples of the cyclotron frequency split into peaks.

Calculated coefficients agree with experimental observations.

Abstract

The photogalvanic effect is studied in electron gas over the liquid He surface with the presence of quantizing magnetic field. The gas is affected by the weak alternating microwave electric field tilted towards the surface normal. Both linear and circular photogalvanic effects are studied. The current occurs via indirect phototransition with the participation of ripplons emission or absorption. The photogalvanic tensor has strong resonances at the microwave frequency $\omega$ approaching to the frequencies of transitions between size-quantized subbands. The resonances are symmetric or antisymmetric, depending on a tensor component. Other resonances appear at $\omega\approx n \omega_c$, where $n$ being integer and $\omega_c$ is the cyclotron frequency. It is found that the latter resonances split to two peaks connected with emission or absorption of ripplons. The calculated photogalvanic coefficients are in accord with the experimental observed values.