Yu. P. Monarkha

A two-dimensional Wigner crystal (Review Article)

The current state of theoretical and experimental studies of the Wigner crystallization of a two-dimensional electron gas is reviewed. The Wigner crystal (WC) has first been observed experimentally in a two-dimensional electron system on the surface of liquid helium in 1979. This success was favored by the exceptional purity of the free surface of superfluid liquid and the ability to fairly accurately describe the polaronic deformation phenomena accompanying the crystallization of electrons. Very pure samples of heterostructures (GaAs/GaAlAs) and strong magnetic fields, making easier the localization of electrons in a conducting layer, were necessary in order to observe the Wigner crystallization in semiconductor two-dimensional electron systems This review discusses the basic properties of a two-dimensional WC, common to the both above-mentioned electronic systems, and also major advances in the study of transport properties of WC caused by response of the environment on motion of the electron lattice.

Polarization dependence of microwave-induced magnetoconductivity oscillations in a two-dimensional electron gas on liquid helium

The dependence of radiation-induced dc magnetoconductivity oscillations on the microwave polarization is theoretically studied for a two-dimensional system of strongly interacting electrons formed on the surface of liquid helium. Two different theoretical mechanisms of magnetooscillations (the displacement and inelastic models) are investigated. We found that both models are similarly sensitive to a change of circular polarization, but they respond differently to a change of linear polarization. Theoretical results are compared with the recent observation of a photoconductivity response at cyclotron-resonance harmonics.

Temperature bistability in a 2D electron system on liquid helium induced by Coulomb interaction under cyclotron-resonance excitation

The energy balance of strongly interacting surface electrons on liquid helium under cyclotron-resonance excitation is theoretically studied. The Coulomb interaction is shown to induce temperature bistability of the electron system, if the magnetic field and electron density are high enough. Surprisingly, bistability appears already for quite low average kinetic energies, when nearly all electrons occupy the ground surface subband. The electron temperature Te, as the function of the magnetic field B, exhibits hysteresis and bistability jumps in a certain range of the microwave power. Above the threshold microwave field, the line shape Te(B) is shown to be sensitive to details of the ripplon dispersion at large wave numbers.

Quantum magnetotransport in a highly correlated two-dimensional electron liquid on a superfluid helium surface

The theoretical concept of the inelastic quantum magnetotransport of highly correlated surface electrons on superfluid helium is presented. The low-temperature magnetoconductivity data are obtained from the damping of the edge magnetoplasmons. It is shown that the temperature and magnetic field dependences of the magnetoconductivity can be perfectly described by the inelastic many-electron theory as the interplay of two kinds of Landau level broadening produced by scatterers and by mutual Coulomb interaction.

Surface phenomena in microstratified He3He4 solution

Abstract Surface phenomena in the He 3 He 4 solution, whose free surface contains a thin, though macroscopic film rich in He 3 are studied theoretically. The surface excitation spectrum of such microstratified solution is shown to have two branches - one corresponds to usual ripplons and the other is a new sound mode (the third surface sound) in the long wavelength limit and corresponds to the thickness variation in the He 3 -rich film. The possibility of applying low - dimensional electron systems existing in helium to practical studies of surface phenomena in microstratified solutions is considered.