2,594 research outputs found
Co-planar spin-polarized light emitting diode
Studies of spin manipulation in semiconductors has benefited from the
possibility to grow these materials in high quality on top of optically active
III-V systems. The induced electroluminescence in these layered semiconductor
heterostructures has been used for a reliable spin detection. In semiconductors
with strong spin-orbit interaction, the sensitivity of vertical devices may be
insufficient, however, because of the sepration of the spin aligner part and
the spin detection region by one or more heterointerfaces and becuse of the
short spin coherence length. Here we demostrate that higly sensitive spin
detection can be achieved using a lateral arrangement of the spin polarized and
optically active regions. Using our co-planar spin-polarized light emitting
diodes we detect electrical field induced spin generation in a semiconductor
heterojunction two-dimensional hole gas. The polarization results from spin
asymmetric recombination of injected electrons with strongly SO coupled
two-dimensional holes. The possibility to detect magnetized Co particles
deposited on the co-planar diode structure is also demonstrated.Comment: 8 pages, 3 figure
Modeling of diffusion of injected electron spins in spin-orbit coupled microchannels
We report on a theoretical study of spin dynamics of an ensemble of
spin-polarized electrons injected in a diffusive microchannel with linear
Rashba and Dresselhaus spin-orbit coupling. We explore the dependence of the
spin-precession and spin-diffusion lengths on the strengths of spin-orbit
interaction and external magnetic fields, microchannel width, and orientation.
Our results are based on numerical Monte Carlo simulations and on approximate
analytical formulas, both treating the spin dynamics quantum-mechanically. We
conclude that spin-diffusion lengths comparable or larger than the
precession-length occur i) in the vicinity of the persistent spin helix regime
for arbitrary channel width, and ii) in channels of similar or smaller width
than the precession length, independent of the ratio of Rashba and Dresselhaus
fields. For similar strengths of the Rashba and Dresselhaus fields, the
steady-state spin-density oscillates or remains constant along the channel for
channels parallel to the in-plane diagonal crystal directions. An oscillatory
spin-polarization pattern tilted by 45 with respect to the channel
axis is predicted for channels along the main cubic crystal directions. For
typical experimental system parameters, magnetic fields of the order of Tesla
are required to affect the spin-diffusion and spin-precession lengths.Comment: Replaced with final version (some explanations and figures improved).
8 pages, 6 figure
Low-dimensional light-emitting transistor with tunable recombination zone
We present experimental and numerical studies of a light-emitting transistor
comprising two quasi-lateral junctions between a two-dimensional electron and
hole gas. These lithographically defined junctions are fabricated by etching of
a modulation doped GaAs/AlGaAs heterostructure. In this device electrons and
holes can be directed to the same area by drain and gate voltages, defining a
recombination zone tunable in size and position. It could therefore provide an
architecture for probing low-dimensional devices by analysing the emitted light
of the recombination zone.Comment: 12 Pages, to be published in Journal of Modern Optic
Experimental observation of the spin-Hall effect in a two dimensional spin-orbit coupled semiconductor system
We report the experimental observation of the spin-Hall effect in a
two-dimensional (2D) hole system with Rashba spin-orbit coupling.
The 2D hole layer is a part of a p-n junction light-emitting diode with a
specially designed co-planar geometry which allows an angle-resolved
polarization detection at opposite edges of the 2D hole system. In equilibrium
the angular momenta of the Rashba split heavy hole states lie in the plane of
the 2D layer. When an electric field is applied across the hole channel a non
zero out-of-plane component of the angular momentum is detected whose sign
depends on the sign of the electric field and is opposite for the two edges.
Microscopic quantum transport calculations show only a weak effect of disorder
suggesting that the clean limit spin-Hall conductance description (intrinsic
spin-Hall effect) might apply to our system.Comment: 4 pages, 3 figures, paper based on work presented at the Gordon
Research Conference on Magnetic Nano-structures (August 2004) and Oxford Kobe
Seminar on Spintronics (September 2004); accepted for publication in Physical
Review Letters December 200
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