530 research outputs found
Spin relaxation in Rashba rings
Spin relaxation dynamics in rings with Rashba spin-orbit coupling is
investigated using spin kinetic equation. We find that the spin relaxation in
rings occurs toward a persistent spin configuration whose final shape depends
on the initial spin polarization profile. As an example, it is shown that a
homogeneous parallel to the ring axis spin polarization transforms into a
persistent crown-like spin structure. It is demonstrated that the ring geometry
introduces a geometrical contribution to the spin relaxation rate speeding up
the transient dynamics. Moreover, we identify several persistent spin
configurations as well as calculate the Green function of spin kinetic
equation
Dynamics of Spin Relaxation near the Edge of Two-Dimensional Electron Gas
We report calculations of spin relaxation dynamics of two-dimensional
electron gas with spin-orbit interaction at the edge region. It is found that
the relaxation of spin polarization near the edge is more slow than relaxation
in the bulk. That results finally in the spin accumulation at the edge. Time
dependence of spin polarization density is calculated analytically and
numerically. The mechanism of slower spin relaxation near the edge is related
to electrons reflections from the boundary and the lack of the translation
symmetry. These reflections partially compensate electron spin precession
generated by spin-orbit interaction, consequently making the spin polarization
near the edge long living. This effect is accompanied by spin polarization
oscillations and spin polarization transfer from the perpendicular to in-plane
component
Spin Photovoltaic Effect in Quantum Wires with Rashba Interaction
We propose a mechanism for spin polarized photocurrent generation in quantum
wires. The effect is due to the combined effect of Rashba spin-orbit
interaction, external magnetic field and microwave radiation. The
time-independent interactions in the wire give rise to a spectrum asymmetry in
k-space. The microwave radiation induces transitions between spin-splitted
subbands, and, due to the peculiar energy dispersion relation, charge and spin
currents are generated at zero bias voltage. We demonstrate that the generation
of pure spin currents is possible under an appropriate choice of external
control parameters
Radiation-induced current in quantum wires with side-coupled nano-rings
Photocurrent generation is studied in a system composed of a quantum wire
with side-coupled quantum rings. The current generation results from the
interplay of the particular geometry of the system and the use of circularly
polarized radiation. We study the energy-momentum conservation for optical
transitions involving electrons moving forwards and backwards in the wire. Due
to the lack of time-reversal symmetry in the radiation, the optical transitions
depend on the direction of motion of the electrons, leading to a current at
zero bias voltage. The photocurrent increases with the number of rings within a
wide range of physical parameters. A weak non-linear dependence of the current
in the number of rings, related to quantum interference effects, is also
predicted. This geometry suggests a scalable method for the generation of
sizeable photocurrents based on nanoscale components.Comment: 7 pages, 6 figure
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