6 research outputs found
Anisotropic universal conductance fluctuations in disordered quantum wires with Rashba and Dresselhaus spin-orbit interaction and applied in-plane magnetic field
We investigate the transport properties of narrow quantum wires realized in
disordered two-dimensional electron gases in the presence of k-linear Rashba
and Dresselhaus spin-orbit interaction (SOI), and an applied in-plane magnetic
field. Building on previous work [Scheid, et al., PRL 101, 266401 (2008)], we
find that in addition to the conductance, the universal conductance
fluctuations also feature anisotropy with respect to the magnetic field
direction. This anisotropy can be explained solely from the symmetries
exhibited by the Hamiltonian as well as the relative strengths of the Rashba
and Dresselhaus spin orbit interaction and thus can be utilized to detect this
ratio from purely electrical measurements.Comment: 10 pages, 4 figures, 1 tabl
Extracting current-induced spins: spin boundary conditions at narrow Hall contacts
We consider the possibility to extract spins that are generated by an
electric current in a two-dimensional electron gas with Rashba-Dresselhaus
spin-orbit interaction (R2DEG) in the Hall geometry. To this end, we discuss
boundary conditions for the spin accumulations between a spin-orbit coupled
region and contact without spin-orbit coupling, i.e. a normal two-dimensional
electron gas (2DEG). We demonstrate that in contrast to contacts that extend
along the whole sample, a spin accumulation can diffuse into the normal region
through finite contacts and detected by e.g. ferromagnets. For an
impedance-matched narrow contact the spin accumulation in the 2DEG is equal to
the current induced spin accumulation in the bulk of R2DEG up to a
geometry-dependent numerical factor.Comment: 18 pages, 7 figures, submitted to NJP focus issue on Spintronic
Spin Accumulation in Diffusive Conductors with Rashba and Dresselhaus Spin-Orbit Interaction
We calculate the electrically induced spin accumulation in diffusive systems
due to both Rashba (with strength and Dresselhaus (with strength
spin-orbit interaction. Using a diffusion equation approach we find
that magnetoelectric effects disappear and that there is thus no spin
accumulation when both interactions have the same strength, .
In thermodynamically large systems, the finite spin accumulation predicted by
Chaplik, Entin and Magarill, [Physica E {\bf 13}, 744 (2002)] and by Trushin
and Schliemann [Phys. Rev. B {\bf 75}, 155323 (2007)] is recovered an
infinitesimally small distance away from the singular point .
We show however that the singularity is broadened and that the suppression of
spin accumulation becomes physically relevant (i) in finite-sized systems of
size , (ii) in the presence of a cubic Dresselhaus interaction of strength
, or (iii) for finite frequency measurements. We obtain the parametric
range over which the magnetoelectric effect is suppressed in these three
instances as (i) , (ii), and (iii) |\alpha|-|\beta| \lesssiM
\sqrt{\omega/m p_{\rm F}\ell} with the elastic mean free path and
the Fermi momentum. We attribute the absence of spin accumulation
close to to the underlying U (1) symmetry. We illustrate and
confirm our predictions numerically
Semiconductor Spintronics
Spintronics refers commonly to phenomena in which the spin of electrons in a
solid state environment plays the determining role. In a more narrow sense
spintronics is an emerging research field of electronics: spintronics devices
are based on a spin control of electronics, or on an electrical and optical
control of spin or magnetism. This review presents selected themes of
semiconductor spintronics, introducing important concepts in spin transport,
spin injection, Silsbee-Johnson spin-charge coupling, and spindependent
tunneling, as well as spin relaxation and spin dynamics. The most fundamental
spin-dependent nteraction in nonmagnetic semiconductors is spin-orbit coupling.
Depending on the crystal symmetries of the material, as well as on the
structural properties of semiconductor based heterostructures, the spin-orbit
coupling takes on different functional forms, giving a nice playground of
effective spin-orbit Hamiltonians. The effective Hamiltonians for the most
relevant classes of materials and heterostructures are derived here from
realistic electronic band structure descriptions. Most semiconductor device
systems are still theoretical concepts, waiting for experimental
demonstrations. A review of selected proposed, and a few demonstrated devices
is presented, with detailed description of two important classes: magnetic
resonant tunnel structures and bipolar magnetic diodes and transistors. In most
cases the presentation is of tutorial style, introducing the essential
theoretical formalism at an accessible level, with case-study-like
illustrations of actual experimental results, as well as with brief reviews of
relevant recent achievements in the field.Comment: tutorial review; 342 pages, 132 figure
Geometric Correlations and Breakdown of Mesoscopic Universality in Spin Transport
We construct a unified semiclassical theory of charge and spin transport in chaotic ballistic and disordered diffusive mesoscopic systems with spin-orbit interaction. Neglecting dynamic effects of spin-orbit interaction, we reproduce the random matrix theory results that the spin conductance fluctuates universally around zero average. Incorporating these effects into the theory, we show that geometric correlations generate finite average spin conductances, but that they do not affect the charge conductance to leading order. The theory, which is confirmed by numerical transport calculations, allows us to investigate the entire range from the weak to the previously unexplored strong spin-orbit regime, where the spin rotation time is shorter than the momentum relaxation time