A. N. Kalinenko

Effects of electron-electron scattering on electron-beam propagation in a two-dimensional electron gas

We have studied experimentally and theoretically the influence of electron-electron collisions on the propagation of electron beams in a two-dimensional electron gas for excess injection energies ranging from zero up to the Fermi energy. We find that the detector signal consists of quasiballistic electrons, which either have not undergone any electron-electron collisions or have only been scattered at small angles. Theoretically, the small-angle scattering exhibits distinct features that can be traced back to the reduced dimensionality of the electron system. A number of nonlinear effects, also related to the two-dimensional character of the system, are discussed. In the simplest situation, the heating of the electron gas by the high-energy part of the beam leads to a weakening of the signal of quasiballistic electrons and to the appearance of thermovoltage. This results in a nonmonotonic dependence of the detector signal on the intensity of the injected beam, as observed experimentally.

The theory of kinetic effects in two-dimensional degenerate gas of colliding electrons

A mathematical method based on a reduced representation of the electron–electron collision operator acting in the space of quasi-equilibrium functions is constructed. A number of kinetic phenomena such as the evolution of highly anisotropic and high-energy electron distributions, the quasi-hydrodynamic effect in electrical conduction, and a new nonlinear transport mode are described from a unified point of view. Kinetic effects which can be observed in experiments on electron beam propagation and electrical conduction of (GaAs)Al wires with a high mobility of charge carriers are predicted.

Spin-transport effects in electron systems on liquid helium surfaces

Transport phenomena are examined in electron systems on liquid helium surfaces in strong nonquantizing nonuniform magnetic fields. For applied electric fields with frequencies low enough that an equilibrium distribution of the spins along the conducting surface can develop during the wave period, the electrical resistance is determined by different current carrier scattering processes than in the uniform case. Spin nonuniformity makes electron-electron collisions efficient with respect to momentum loss, so that galvanomagnetic effects differ substantially from the Drude-Lorentz theory. A nonstationary spin-electron effect is found in a direction perpendicular to the applied electric field. The evolution of the transport properties following application of a nonuniform magnetic field is discussed.

Nonmagnetic spinguides and spin transport in semiconductors

The construction of a spinguide—a semiconductor channel with walls consisting of a dilute magnetic semiconductor with very large Zeeman splitting and transmitting electrons only with one type of polarization—is proposed. Such channels can be sources of spin-polarized current in nonmagnetic conductors. They can be used for creating fast switches of the spin-polarization direction of the electric current and for transmitting spin polarization over large distances (even larger than the spin-flip length). The selective transparency of the walls gives rise to new size transport effects.

On dynamic properties of a two-dimensional degenerate electron gas

A detailed theory of electron–electron scattering in two-dimensional degenerate systems in heterostructures is constructed as a result of analysis and numerical computations. The conditions are formulated and the values of characteristic parameters are obtained for which specific two-dimensional effects predicted earlier from theoretical considerations can be observed. New properties of scattering indicatrix, viz., a beam of electrons flying almost antiparallel to the primary beam and a very narrow beam of holes flying in the forward direction, are found.

Equilibrium and quasi-equilibrium spin-electrical effect in the system of electrons floating on the surface of liquid helium

It is shown that a potential difference, the value of which depends on the spin state of electrons, appears in the vicinity of the system of electrons floating on the surface of liquid helium in an inhomogeneous magnetic field.

The distinctions between the electrical conductivities under non-contact and contact current excitation in spin–split two-dimensional conductors

Abstract It is shown that the normal electron–electron scattering is a source of electrical resistance on non-contact current excitation in two-dimensional spin–split electron systems. In contrast to the contact current injection, non-contact current excitation causes spatially inhomogeneous polarization in a two-dimensional conductor leading to new resistivity mechanisms.

Influence of electron-electron scattering on spin-polarized current states in magnetically wrapped nanowires*

The role of electron–electron collisions in the formation of spin-polarized current states in a spin guide—a system consisting of a nonmagnetic conducting channel wrapped in a grounded nanoscale magnetic shell—is studied. It is shown that under certain conditions the spin guide can generate and transport nonequilibrium electron density with high spin polarization over long distances even though frequent electron–electron scattering causes drifting of the nonequilibrium electrons as a whole. Ways to convert the spin-polarized electron density into a spin-polarized electric current are proposed.

Electron–electron scattering and the propagation of electron beams in a two-dimensional electron gas

Experimental studies of electron-beam propagation in a degenerate 2DEG in a GaAs-(Al,Ga)As heterostructure are presented for a wide range of injection energies, 0<E⩽EF. The electron beam is injected and detected in the 2DEG via electrostatically defined quantum point-contacts with typical distances of 3.4μm. Energy-dependent beam injection is used to reveal the characteristics of the electron-beam propagation. Considering the specific character for electron–electron scattering events in 2D systems linearized Boltzmann equations could be used to model the experimental observations.

Electrical resistance of spatially varying magnetic interfaces. The role of normal scattering

We investigate the diffusive electron transport in conductors with spatially inhomogeneous magnetic properties taking into account both impurity and normal scattering. It is found that the additional interface resistance that arises due to the magnetic inhomogeneity depends essentially on their spatial characteristics. The resistance is proportional to the spin flip time in the case when the magnetic properties of the conducting system vary smoothly enough along the sample. It can be used to direct experimental investigation of spin flip processes. In the opposite case, when magnetic characteristics are varied sharply, the additional resistance depends essentially on the difference of magnetic properties of the sides far from the interface region. The resistance increases as the frequency of the electron-electron scattering increases. We consider also two types of smooth interfaces: (i) between fully spin-polarized magnetics and usual magnetic (or non-magnetic) conductors, and (ii) between two fully oppositely polarized magnetic conductors. It is shown that the interface resistance is very sensitive to appearing of the fully spin-polarized state under the applied external field.We investigate the diffusive electron transport in conductors with spatially inhomogeneous magnetic properties taking into account both impurity and normal scattering. It is found that the additional interface resistance that arises due to the magnetic inhomogeneity depends essentially on their spatial characteristics. The resistance is proportional to the spin flip time in the case when the magnetic properties of the conducting system vary smoothly enough along the sample. It can be used to direct experimental investigation of spin flip processes. In the opposite case, when magnetic characteristics are varied sharply, the additional resistance depends essentially on the difference of magnetic properties of the sides far from the interface region. The resistance increases as the frequency of the electron-electron scattering increases. We consider also two types of smooth interfaces: (i) between fully spin-polarized magnetics and usual magnetic (or non-magnetic) conductors, and (ii) between two fully oppositely polarized magnetic conductors. It is shown that the interface resistance is very sensitive to appearing of the fully spin-polarized state under the applied external field.