114 research outputs found
Electron Spin Injection at a Schottky Contact
We investigate theoretically electrical spin injection at a Schottky contact
between a spin-polarized electrode and a non-magnetic semiconductor. Current
and electron density spin-polarizations are discussed as functions of barrier
energy and semiconductor doping density. The effect of a spin-dependent
interface resistance that results from a tunneling region at the
contact/semiconductor interface is described. The model can serve as a guide
for designing spin-injection experiments with regard to the interface
properties and device structure.Comment: 4 pages, 4 figure
Modelling of Optical Detection of Spin-Polarized Carrier Injection into Light-Emitting Devices
We investigate the emission of multimodal polarized light from Light Emitting
Devices due to spin-aligned carriers injection. The results are derived through
operator Langevin equations, which include thermal and carrier-injection
fluctuations, as well as non-radiative recombination and electronic g-factor
temperature dependence. We study the dynamics of the optoelectronic processes
and show how the temperature-dependent g-factor and magnetic field affect the
polarization degree of the emitted light. In addition, at high temperatures,
thermal fluctuation reduces the efficiency of the optoelectronic detection
method for measuring spin-polarization degree of carrier injection into
non-magnetic semicondutors.Comment: 15 pages, 7 figures, replaced by revised version. To appear in Phys.
Rev.
Spin injection through the depletion layer: a theory of spin-polarized p-n junctions and solar cells
A drift-diffusion model for spin-charge transport in spin-polarized {\it p-n}
junctions is developed and solved numerically for a realistic set of material
parameters based on GaAs. It is demonstrated that spin polarization can be
injected through the depletion layer by both minority and majority carriers,
making all-semiconductor devices such as spin-polarized solar cells and bipolar
transistors feasible. Spin-polarized {\it p-n} junctions allow for
spin-polarized current generation, spin amplification, voltage control of spin
polarization, and a significant extension of spin diffusion range.Comment: 4 pages, 3 figure
Electric-field dependent spin diffusion and spin injection into semiconductors
We derive a drift-diffusion equation for spin polarization in semiconductors
by consistently taking into account electric-field effects and nondegenerate
electron statistics. We identify a high-field diffusive regime which has no
analogue in metals. In this regime there are two distinct spin diffusion
lengths. Furthermore, spin injection from a ferromagnetic metal into a
semiconductor is enhanced by several orders of magnitude and spins can be
transported over distances much greater than the low-field spin diffusion
length.Comment: 5 pages, 3 eps figure
Spin oscillations in transient diffusion of a spin pulse in n-type semiconductor quantum wells
By studying the time and spatial evolution of a pulse of the spin
polarization in -type semiconductor quantum wells, we highlight the
importance of the off-diagonal spin coherence in spin diffusion and transport.
Spin oscillations and spin polarization reverse along the the direction of spin
diffusion in the absence of the applied magnetic field are predicted from our
investigation.Comment: 5 pages, 4 figures, accepted for publication in PR
Mesoscopic Stern-Gerlach device to polarize spin currents
Spin preparation and spin detection are fundamental problems in spintronics
and in several solid state proposals for quantum information processing. Here
we propose the mesoscopic equivalent of an optical polarizing beam splitter
(PBS). This interferometric device uses non-dispersive phases (Aharonov-Bohm
and Rashba) in order to separate spin up and spin down carriers into distinct
outputs and thus it is analogous to a Stern-Gerlach apparatus. It can be used
both as a spin preparation device and as a spin measuring device by converting
spin into charge (orbital) degrees of freedom. An important feature of the
proposed spin polarizer is that no ferromagnetic contacts are used.Comment: Updated to the published versio
First-principles study of nucleation, growth, and interface structure of Fe/GaAs
We use density-functional theory to describe the initial stages of Fe film
growth on GaAs(001), focusing on the interplay between chemistry and magnetism
at the interface. Four features appear to be generic: (1) At submonolayer
coverages, a strong chemical interaction between Fe and substrate atoms leads
to substitutional adsorption and intermixing. (2) For films of several
monolayers and more, atomically abrupt interfaces are energetically favored.
(3) For Fe films over a range of thicknesses, both Ga- and As-adlayers
dramatically reduce the formation energies of the films, suggesting a
surfactant-like action. (4) During the first few monolayers of growth, Ga or As
atoms are likely to be liberated from the interface and diffuse to the Fe film
surface. Magnetism plays an important auxiliary role for these processes, even
in the dilute limit of atomic adsorption. Most of the films exhibit
ferromagnetic order even at half-monolayer coverage, while certain
adlayer-capped films show a slight preference for antiferromagnetic order.Comment: 11 two-column pages, 12 figures, to appear in Phys. Rev.
Erratum: "A Gravitational-wave Measurement of the Hubble Constant Following the Second Observing Run of Advanced LIGO and Virgo" (2021, ApJ, 909, 218)
[no abstract available
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