Piezoelectric mechanism of orientation of a bilayer Wigner crystal in a GaAs matrix

A mechanism for orientation of bilayer classical Wigner crystals in a piezoelectric medium is considered. For the GaAs system the piezoelectric correction to the electrostatic interaction between electrons is calculated. It is shown that taking into account the correction due to the piezoelectric effect leads to a dependence of the total energy of the electron crystal on its orientation with respect to the crystallographic axes of the surrounding matrix. A generalization of Ewald's method is obtained for calculating the anisotropic interaction between electrons in a Wigner crystal. The method is used to calculate the energy of bilayer Wigner crystals in electron layers parallel to the crystallographic planes (001), (0-11), and (111) as a function of their orientation and the distance between layers, and the energetically most favorable orientation for all types of electron lattices in a bilayer system is found. It is shown that phase transitions between structures with different lattice symmetry in a Wigner crystal can be accompanied by a change of its orientation.Comment: 11 pages, 4 eps figures include

Magnetoresistance of nondegenerate quantum electron channels formed on the surface of superfluid helium

Transport properties of quasi-one-dimensional nondegenerate quantum wires formed on the surface of liquid helium in the presence of a normal magnetic field are studied using the momentum balance equation method and the memory function formalism. The interaction with both kinds of scatterers available (vapor atoms and capillary wave quanta) is considered. We show that unlike classical wires, quantum nondegenerate channels exhibit strong magnetoresistance which increases with lowering the temperature.Comment: 8 pages, 7 figure

Nonlinear surface electron transport over liquid helium

We present experimental data and a theoretical analysis of nonequilibrium mobility of surface electrons in liquid helium. The experiments are carried out in the temperature range where electron mobility is limited by electron scattering at surface excitations of liquid helium (ripplons). Holding and driving electric fields of wide ranges are used in measurements. Special attention is paid to the condition of strong holding fields under which hot electrons are confined to the ground surface level. Depending on the relation between the momentum relaxation rate and electron–electron collision frequency, different theoretical approaches are used to describe the nonlinear mobility of surface electrons. The results obtained allow to estimate the range of physical parameters where experimental data can be described by the theory of nonlinear electron transport within the ground surface level