Circular-Polarization-Dependent Study of Microwave-Induced Conductivity Oscillations in a Two-Dimensional Electron Gas on Liquid Helium.

The polarization dependence of the photoconductivity response at cyclotron-resonance harmonics in a nondegenerate two-dimensional (2D) electron system formed on the surface of liquid helium is studied using a setup in which a circular polarization of opposite directions can be produced. Contrary to the results of similar investigations reported for semiconductor 2D electron systems, for electrons on liquid helium, a strong dependence of the amplitude of magnetoconductivity oscillations on the direction of circular polarization is observed. This observation is in accordance with theoretical models based on photon-assisted scattering, and, therefore, it presents a principal argument in the dispute over the origin of microwave-induced conductivity oscillations.

Anomalous Quasiparticle Reflection from the Surface of a ^{3}He-^{4}He Dilute Solution.

A free surface of a dilute ^{3}He-^{4}He liquid mixture is a unique system where two Fermi liquids with distinct dimensions coexist: a three-dimensional (3D) ^{3}He Fermi liquid in the bulk and a two-dimensional (2D) ^{3}He Fermi liquid at the surface. To investigate a novel effect generated by the interaction between the two Fermi liquids, the mobility of a Wigner crystal of electrons formed on the free surface of the mixture is studied. An anomalous enhancement of the mobility, compared with the case where the 3D and 2D systems do not interact with each other, is observed.

Photoconductivity Response at Cyclotron-Resonance Harmonics in a Nondegenerate Two-Dimensional Electron Gas on Liquid Helium.

We report the first observation of an oscillatory photoconductivity response at the cyclotron-resonance harmonics in a nondegenerate 2D electron system formed on the free surface of liquid helium. The dc conductivity oscillations are detected for electrons occupying the ground surface subband. Their period is governed by the ratio of the microwave frequency to the cyclotron frequency.

Nonlinear Wigner solid transport on the free surface of normal and superfluid 3He.

We present measurements and a theoretical concept of the nonlinear transport in the two-dimensional Wigner solid on the free surface of normal and superfluid 3He. We have observed the transition from Ohmic to nonlinear transport over a wide temperature range, from 200 microK to 200 mK at low electron velocities. The field-velocity (E-nu) characteristics show a nonmonotonic structure with a particular local maxima.