226 research outputs found
Harper-Hofstadter problem for 2D electron gas with -linear Rashba spin-orbit coupling
The Harper-Hofstadter problem for two-dimensional electron gas with Rashba
spin-orbit coupling subject to periodic potential and perpendicular magnetic
field is studied analytically and numerically. The butterfly-like energy
spectrum, spinor wave functions as well as the spin density and average spin
polarization are calculated for actual parameters of semiconductor structure.
Our calculations show that in two-dimensional electron gas subject to periodic
potential and uniform magnetic field the effects of energy spectrum splitting
caused by large spin-orbit Rashba coupling can be observed experimentally.Comment: 8 pages, 6 figures. submitted to Europhys. Letter
Evanescent states in 2D electron systems with spin-orbit interaction and spin-dependent transmission through a barrier
We find that the total spectrum of electron states in a bounded 2D electron
gas with spin-orbit interaction contains two types of evanescent states lying
in different energy ranges. The first-type states fill in a gap, which opens in
the band of propagating spin-splitted states if tangential momentum is nonzero.
They are described by a pure imaginary wavevector. The states of second type
lie in the forbidden band. They are described by a complex wavevector. These
states give rise to unusual features of the electron transmission through a
lateral potential barrier with spin-orbit interaction, such as an oscillatory
dependence of the tunneling coefficient on the barrier width and electron
energy. But of most interest is the spin polarization of an unpolarized
incident electron flow. Particularly, the transmitted electron current acquires
spin polarization even if the distribution function of incident electrons is
symmetric with respect to the transverse momentum. The polarization efficiency
is an oscillatory function of the barrier width. Spin filtering is most
effective, if the Fermi energy is close to the barrier height.Comment: 9 pages, 9 figures, more general boundary conditions are used, typos
correcte
Spin current injection by intersubband transitions in quantum wells
We show that a pure spin current can be injected in quantum wells by the
absorption of linearly polarized infrared radiation, leading to transitions
between subbands. The magnitude and the direction of the spin current depend on
the Dresselhaus and Rashba spin-orbit coupling constants and light frequency
and, therefore, can be manipulated by changing the light frequency and/or
applying an external bias across the quantum well. The injected spin current
should be observable either as a voltage generated via the anomalous spin-Hall
effect, or by spatially resolved pump-probe optical spectroscopy.Comment: minor changes, short version publishe
Ultra-fast spin avalanches in crystals of molecular magnets in terms of magnetic detonation
Recent experiments (Decelle et al., Phys. Rev. Lett. 102, 027203 (2009))
discovered an ultra-fast regime of spin avalanches in crystals of magnetic
magnets, which was three orders of magnitude faster than the traditionally
studied magnetic deflagration. The new regime has been hypothetically
identified as magnetic detonation. Here we demonstrate the possibility of
magnetic detonation in the crystals, as a front consisting of a leading shock
and a zone of Zeeman energy release. We study the dependence of the magnetic
detonation parameters on the applied magnetic field. We find that the magnetic
detonation speed only slightly exceeds the sound speed in agreement with the
experimental observations.Comment: 4 pages, 4 figure
Fast electrochemical doping due to front instability in organic semiconductors
The electrochemical doping transformation in organic semiconductor devices is
studied in application to light-emitting cells. It is shown that the device
performance can be significantly improved by utilizing new fundamental
properties of the doping process. We obtain an instability, which distorts the
doping fronts and increases the doping rate considerably. We explain the
physical mechanism of the instability, develop theory, provide experimental
evidence, and perform numerical simulations. We further show how improved
device design can amplify the instability thus leading to a much faster doping
process and device kinetics.Comment: 4 pages, 4 figure
Robust to impurity-scattering spin Hall effect in two-dimensional electron gas
We propose a mechanism of spin Hall effect in two-dimensional electron gas
with spatially random Rashba spin-orbit interaction. The calculations based on
the Kubo formalism and kinetic equation show that in contrast to the constant
spin-orbit coupling, spin Hall conductivity in the random spin-orbit field is
not totally suppressed by the potential impurity scattering. Even if the
regular contribution is removed by the vertex corrections, the terms we
consider, remain. Therefore, the intrinsic spin-Hall effect exists being,
however, non-universal.Comment: 4+ pages, 2 figure
Physical Limits of the ballistic and non-ballistic Spin-Field-Effect Transistor: Spin Dynamics in Remote Doped Structures
We investigate the spin dynamics and relaxation in remotely-doped two
dimensional electron systems where the dopants lead to random fluctuations of
the Rashba spin-orbit coupling. Due to the resulting random spin precession,
the spin relaxation time is limited by the strength and spatial scale of the
random contribution to the spin-orbit coupling. We concentrate on the role of
the randomness for two systems where the direction of the spin-orbit field does
not depend on the electron momentum: the spin field-effect transistor with
balanced Rashba and Dresselhaus couplings and the (011) quantum well. Both of
these systems are considered as promising for the spintronics applications
because of the suppression of the Dyakonov-Perel' mechanism there makes the
realization of a spin field effect transistor in the diffusive regime possible.
We demonstrate that the spin relaxation through the randomness of spin-orbit
coupling imposes important physical limitations on the operational properties
of these devices.Comment: 10 pages, 4 figure
Cyclotron effect on coherent spin precession of two-dimensional electrons
We investigate the spin dynamics of high-mobility two-dimensional electrons
in GaAs/AlGaAs quantum wells grown along the and directions by
time-resolved Faraday rotation at low temperatures. In measurements on the
-grown structures without external magnetic fields, we observe coherent
oscillations of the electron spin polarization about the effective spin-orbit
field. In non-quantizing magnetic fields applied normal to the sample plane,
the cyclotron motion of the electrons rotates the effective spin-orbit field.
This rotation leads to fast oscillations in the spin polarization about a
non-zero value and a strong increase in the spin dephasing time in our
experiments. These two effects are absent in the -grown structure due to
the different symmetry of its effective spin-orbit field. The measurements are
in excellent agreement with our theoretical model.Comment: 4 pages, 3 figure
Coherent spin dynamics in quantum wells in quantizing magnetic field
We investigate theoretically the coherent longitudinal and transversal spin
relaxation of photoexcited electrons in quantum wells in quantized magnetic
fields. We find the relaxation time for typical quantum well parameters between
100 and 1000 ps. For a realistic random potential the relaxation process
depends on the electron energy and g-factor, demonstrating oscillations in the
spin polarization accompanying the spin relaxation. The dependence of spin
relaxation on applied field, and thus on the corresponding "magnetic" length,
can be used to characterize the spatial scale of disorder in quantum wells.Comment: 13 pages, 4 figure
Nonlinear equation for curved stationary flames
A nonlinear equation describing curved stationary flames with arbitrary gas
expansion , subject to the
Landau-Darrieus instability, is obtained in a closed form without an assumption
of weak nonlinearity. It is proved that in the scope of the asymptotic
expansion for the new equation gives the true solution to the
problem of stationary flame propagation with the accuracy of the sixth order in
In particular, it reproduces the stationary version of the
well-known Sivashinsky equation at the second order corresponding to the
approximation of zero vorticity production. At higher orders, the new equation
describes influence of the vorticity drift behind the flame front on the front
structure. Its asymptotic expansion is carried out explicitly, and the
resulting equation is solved analytically at the third order. For arbitrary
values of the highly nonlinear regime of fast flow burning is
investigated, for which case a large flame velocity expansion of the nonlinear
equation is proposed.Comment: 29 pages 4 figures LaTe
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