A. V. Yanovsky

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.

Dynamics of a spin-polarized electron liquid: Spin oscillations with a low decay

We investigate the dynamics of spin-nonequilibrium electron systems for the case when normal electron collisions prevail over the other scattering processes and the ”hydrodynamic flow” regime is realized. The hydrodynamic equations for the electron liquid have been obtained and analyzed. We demonstrate that oscillations of the spin polarization are possible in a conducting ring with inhomogeneous magnetic properties. These low-decay oscillations are accompanied by the oscillations of the drift current in the ring. We demonstrate also that the spin polarization of the electron density may be revealed via the voltage between the ends of the open circuit with an inhomogeneous spin polarization. The effect may be observed both in the hydrodynamic and diffusive regimes. 1 ar X iv :1 10 9. 18 72 v1 [ co nd -m at .m es -h al l] 9 S ep 2 01 1 Dynamics of Spin-Polarized Electron Liquid and Spin Pendulum R.N.Gurzhi, A.N.Kalinenko, A.I.Kopeliovich, P.V.Pyshkin, A.V.Yanovsky

Angle-resolved spectroscopy of electron-electron scattering in a 2D system

Electron-beam propagation experiments have been used to determine the energy and angle dependence of electron-electron (ee) scattering in a two-dimensional electron gas (2DEG) in a very direct manner. The experimental results provide direct evidence for novel ee-scattering effects in 2D degenerate conductors. Most striking is the increased importance of small-angle scattering in a 2D system with decreasing excitation energy. In particular, in a 2DEG ee-scattering can, at sufficiently low energies, be purely dephasing in character, i.e. changing the phase but not the direction of electron motion.

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.

Spin-Polarized Current in a Nonmagnetic Conductor and the Role of Electron–Electron Scattering

The influence of electron–electron scattering on the efficiency of certain methods for the injection and generation of spin–polarized current states in nonmagnetic conductors is discussed. We consider the effect of electron–electron collisions on the resistance to electric transport developing at the interface between a magnetic conductor (MC) and a nonmagnetic conductor (NMC). An essentially unbounded increase of the interfacial MC/NMC magnetoresistance with temperature is predicted.

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.

Spin field-effect transistor with electric control

The effects of spin polarization control in hybrid magnetic-nonmagnetic conductor structures have been considered. The concept of a transistor capable of generating and amplifying a spin-alternating signal has been proposed. The transistor principle is based on spatial separation of spin components and their control with electric gates in the “current-in-plane” hybrid magnetic-nonmagnetic conductor structure. This control is achieved through the effect of spin-electric signal transformation predicted in this study. Such transistor is feasible on the grounds of present-day materials and technologies.

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.

Thomas precession, persistent spin currents and quantum forces

We consider T-invariant spin currents induced by spin-orbit interactions which originate from the confined motion of spin carriers in nanostructures. The resulting Thomas spin precession is a fundamental and purely kinematic relativistic effect occurring when the acceleration of carriers is not parallel to their velocity. In the case where the carriers (e.g. electrons) have magnetic moment, the forces due to the electric field of the spin current can, under certain conditions, exceed the van der Waals-Casimir forces by several orders of magnitude. We also discuss a possible experimental set-up tailored to use these forces for checking the existence of a non-zero anomalous magnetic moment of the photon.

Effect of winding edge currents

We discuss persistent currents for particles with internal degrees of freedom. The currents arise because of winding properties essential for the chaotic motion of the particles in a confined geometry. The currents do not change the particle concentrations or thermodynamics, similar to the skipping orbits in a magnetic field.