Spin relaxation of conduction electrons in (110)-grown quantum wells

The theory of spin relaxation of conduction electrons is developed for zinc-blende-type quantum wells grown on (110)-oriented substrate. It is shown that, in asymmetric structures, the relaxation of electron spin initially oriented along the growth direction is characterized by two different lifetimes and leads to the appearance of an in-plane spin component. The magnitude and sign of the in-plane component are determined by the structure inversion asymmetry of the quantum well and can be tuned by the gate voltage. In an external magnetic field, the interplay of cyclotron motion of carriers and the Larmor precession of electron spin can result in a nonmonotonic dependence of the spin density on the magnetic field.Comment: 5 pages, 3 figure

Ratchet effects in two-dimensional systems with a lateral periodic potential

Radiation-induced ratchet electric currents have been studied theoretically in graphene with a periodic noncentrosymmetric lateral potential. The ratchet current generated under normal incidence is shown to consist of two contributions, one of them being polarization-independent and proportional to the energy relaxation time, and another controlled solely by elastic scattering processes and sensitive to both the linear and circular polarization of radiation. Two realistic mechanisms of electron scattering in graphene are considered. For short-range defects, the ratchet current is helicity-dependent but independent of the direction of linear polarization. For the Coulomb impurity scattering, the ratchet current is forbidden for the radiation linearly polarized in the plane perpendicular to the lateral-potential modulation direction. For comparison, the ratchet currents in a quantum well with a lateral superlattice are calculated at low temperatures with allowance for the dependence of the momentum relaxation time on the electron energy.Comment: 8 pages, 4 figure

Atomic structure of cascades of atomic displacements in metals and alloys after different types of radiation

Using the methods of field ion microscopy, we studied radiation induced defects on an atomically clean surface and within a subsurface volume of platinum initiated by the interaction of neutron (E > 0.1MeV) and Ar+ beams (E = 30 keV). It is shown that the interaction of fast neutrons (E > 0.1 MeV) F = 6.7-1021 m-2, F = 3.5-1022 m-2 with matter leads to the formation in the amount of platinum such as radiation damage which occur after ion irradiation by beams of charged Ar+ ions with E = 30 keV, F = 1020 ion/m2. They are observed at a depth of about 1.5-2 nm irradiated under the surface of Pt by ions Ar+. Thus, we have carried out modeling of neutron impact with matter when replacing the neutron beam by an ion beam that causes the same radiation damage in the bulk of the material. Experimental results on atomic-spatial investigation of radiative defect formation in surface layers of materials, initiated by neutron bombardment (of Pt, E > 0.1 MeV) and ion implantation (in Cu3Au: E = 40 keV, F = 1020 ion/m2, j = 10-3 A/cm2), are considered. Quantitative estimates obtained for the size, shape, and volume fraction of cascades of atomic displacements formed under various types of irradiation in the surface layers of the materials. It is showing that the average size of radiation clusters after irradiation of platinum to a fast neutron fluence of 6.7-1022 m-2 (E > 0.1 MeV) is about 3.2 nm. The experimentally established average size of a radiation cluster (disordered zone) in the alloy after ion bombardment is 4 ×4 ×1.5 nm.The research was carried out within the state assignment of FASO of Russia (No. 0389-2014-0002), supported in part by RFBR (project No. 15-08-06744-A)

Development of amorphized states in subsurface metal regions under radiation exposure

Modes of radiation exposure for development of amorphized states in subsurface regions of platinum are determined. Diagnostics of the irradiated structure was carried out using the field ion microscopy technique. It is shown that radiation exposure of pure metals with an energy of E = 30 keV under variation of the fluence of the charged argon ion beams by two orders of magnitude (1016 to 1018 ions/cm2) produces a significant effect on the kinetics of defect formation in the subsurface regions of irradiated materials. It is found that the phenomenon of metal amorphization in the subsurface regions occurs up to a sample depth of 12 nm under an increase in the fluence to 1018 ions/cm2 and the above irradiation energies. © 2013 Pleiades Publishing, Ltd

Fabrication of submicrocrystalline structure in solid solutions by radiation-induced phase transition

The method of field ion microscopy was used to study the submicrocrystalline structure of the surface of PdCuAg solid solutions obtained after irradiation with Ar+ ions. It was shown that there are radiationinduced structural phase transitions in the subsurface volume of solid solutions irradiated by gas ions with an energy of 20 keV and a fluence of 1018 ion/cm2. The regimes were determined of radiation treatment of structural alloys Pd50Cu30Ag20 in which a microduplex-type structure with the phases' particle sizes being up to 100 nm with the necessary set of properties arises in the subsurface volume. © 2013 Pleiades Publishing, Ltd

Electron scattering in quantum wells subjected to an in-plane magnetic field

It is shown that the electron scattering by static defects, acoustic or optical phonons in quantum wells subjected to an in-plane magnetic field is asymmetric. The probability of scattering contains terms which are proportional to both the electron wave vector and the magnetic field components. The terms under study are caused by the lack of an inversion center in quantum wells due to structure or bulk inversion asymmetry although they are of pure diamagnetic origin. Such a magnetic field induced asymmetry of scattering can be responsible for a number of phenomena. In particular, the asymmetry of inelastic electron-phonon interaction leads to an electric current flow if only the electron gas is driven out of thermal equilibrium with the crystal lattice.Comment: 5 pages, 1 figur

Deduction of Pure Spin Current from Spin Linear and Circular Photogalvanic Effect in Semiconductor Quantum Wells

We study the spin photogalvanic effect in two-dimensional electron system with structure inversion asymmetry by means of the solution of semiconductor optical Bloch equations. It is shown that a linearly polarized light may inject a pure spin current in spin-splitting conduction bands due to Rashba spin-orbit coupling, while a circularly polarized light may inject spin-dependent photocurrent. We establish an explicit relation between the photocurrent by oblique incidence of a circularly polarized light and the pure spin current by normal incidence of a linearly polarized light such that we can deduce the amplitude of spin current from the measured spin photocurrent experimentally. This method may provide a source of spin current to study spin transport in semiconductors quantitatively