2,035 research outputs found
Comment on ``Spin and cyclotron energies of electrons in GaAs/GaAlAs quantum wells''
In a recent publication, Pfeffer and Zawadzki [cond-mat/0607150; Phys. Rev. B
74, 115309 (2006)] attempted a calculation of electron g factor in III-V
heterostructures. The authors emphasize that their outcome is in strong
discrepancy with our original result [Ivchenko and Kiselev, Sov. Phys.
Semicond. 26, 827 (1992)] and readily conclude that ``the previous theory of
the g factor in heterostructures is inadequate''. We show here that the entire
discrepancy can be tracked down to an additional contribution missing in the
incomplete elimination procedure of Pfeffer and Zawadzki. This mistake equally
affects their ``exact'' and approximate results. When the overlooked terms
stemming from the nondiagonal Zeeman interaction between light hole and
spin-orbit-split valence states are taken into account in the effective
electron dispersion, the results of the both approaches applied to the
three-level kp model become identical.Comment: 5 pages, no figure
Inverse spin galvanic effect in the presence of impurity spin-orbit scattering: a diagrammatic approach
Spin-charge interconversion is currently the focus of intensive experimental
and theoretical research both for its intrinsic interest and for its potential
exploitation in the realization of new spintronic functionalities. Spin-orbit
coupling is one of the key microscopic mechanisms to couple charge currents and
spin polarizations. The Rashba spin-orbit coupling in a two-dimensional
electron gas has been shown to give rise to the inverse spin galvanic effect,
i.e. the generation of a non-equilibrium spin polarization by a charge current.
Whereas the Rashba model may be applied to the interpretation of experimental
results in many cases, in general in a given real physical system spin-orbit
coupling also occurs due other mechanisms such as Dresselhaus bulk inversion
asymmetry and scattering from impurities. In this work we consider the inverse
spin galvanic effect in the presence of Rashba, Dresselhaus and impurity
spin-orbit scattering. We find that the size and form of the inverse spin
galvanic effect is greatly modified by the presence of the various sources of
spin-orbit coupling. Indeed, spin-orbit coupling affects the spin relaxation
time by adding the Elliott-Yafet mechanism to the Dyakonov-Perel and,
furthermore, it changes the non-equilibrium value of the current-induced spin
polarization by introducing a new spin generation torque. We use a diagrammatic
Kubo formula approach to evaluate the spin polarization-charge current response
function. We finally comment about the relevance of our results for the
interpretation of experimental results.Comment: 14 pages, 1 figure, invited paper for a special issue of Condensed
Matter (MDPI) on "Control and Enhancement of Quantum Coherence in
Nanostructured Materials
Resonant Fibonacci Quantum Well Structures
We propose a resonant one-dimensional quasicrystal, namely, a multiple
quantum well (MQW) structure satisfying the Fibonacci-chain rule with the
golden ratio between the long and short inter-well distances. The resonant
Bragg condition is generalized from the periodic to Fibonacci MQWs. A
dispersion equation for exciton-polaritons is derived in the two-wave
approximation, the effective allowed and forbidden bands are found. The
reflection spectra from the proposed structures are calculated as a function of
the well number and detuning from the Bragg condition.Comment: 5 pages, 3 figures, submitted to Phys. Rev.
Spin relaxation of conduction electrons in (110)-grown quantum wells
The theory of spin relaxation of conduction electrons is developed for
zinc-blende-type quantum wells grown on (110)-oriented substrate. It is shown
that, in asymmetric structures, the relaxation of electron spin initially
oriented along the growth direction is characterized by two different lifetimes
and leads to the appearance of an in-plane spin component. The magnitude and
sign of the in-plane component are determined by the structure inversion
asymmetry of the quantum well and can be tuned by the gate voltage. In an
external magnetic field, the interplay of cyclotron motion of carriers and the
Larmor precession of electron spin can result in a nonmonotonic dependence of
the spin density on the magnetic field.Comment: 5 pages, 3 figure
Optical properties of 1D photonic crystals based on multiple-quantum-well structures
A general approach to the analysis of optical properties of photonic crystals
based on multiple-quantum-well structures is developed. The effect of the
polarization state and a non-perpendicular incidence of the electromagnetic
wave is taken into account by introduction of an effective excitonic
susceptibility and an effective optical width of the quantum wells. This
approach is applied to consideration of optical properties of structures with a
pre-engineered break of the translational symmetry. It is shown, in particular,
that a layer with different exciton frequency placed at the middle of an MQW
structure leads to appearance of a resonance suppression of the reflection.Comment: 9 pages, 3 figures, submitted to PR
Influence of bottom topography on integral constraints in zonal flows with parameterized potential vorticity fluxes
An integral constraint for eddy fluxes of potential vorticity (PV), corresponding to global momentum conservation, is applied to two-layer zonal quasi-geostrophic channel flow. This constraint must be satisfied for any type of parameterization of eddy PV fluxes. Bottom topography strongly influence the integral constraint compared to a flat bottom channel. An analytical solution for the mean flow solution has been found by using asymptotic expansion in a small parameter which is the ratio of the Rossby radius to the meridional extent of the channel. Applying the integral constraint to this solution, one can find restrictions for eddy PV transfer coefficients which relate the eddy fluxes of PV to the mean flow. These restrictions strongly deviate from restrictions for the channel with flat bottom topography
Valley Dependent Optoelectronics from Inversion Symmetry Breaking
Inversion symmetry breaking allows contrasted circular dichroism in different
k-space regions, which takes the extreme form of optical selection rules for
interband transitions at high symmetry points. In materials where band-edges
occur at noncentral valleys, this enables valley dependent interplay of
electrons with light of different circular polarizations, in analogy to spin
dependent optical activities in semiconductors. This discovery is in perfect
harmony with the previous finding of valley contrasted Bloch band features of
orbital magnetic moment and Berry curvatures from inversion symmetry breaking
[Phys. Rev. Lett. 99, 236809 (2007)]. A universal connection is revealed
between the k-resolved optical oscillator strength of interband transitions,
the orbital magnetic moment and the Berry curvatures, which also provides a
principle for optical measurement of orbital magnetization and intrinsic
anomalous Hall conductivity in ferromagnetic systems. The general physics is
demonstrated in graphene where inversion symmetry breaking leads to valley
contrasted optical selection rule for interband transitions. We discuss
graphene based valley optoelectronics applications where light polarization
information can be interconverted with electronic information.Comment: Expanded version, to appear in Phys. Rev.
Spin orientation of two-dimensional electron gas under intraband optical pumping
The theory of spin orientation of two-dimensional (2D) electron gas has been
developed for intrasubband indirect optical transitions. The monopolar optical
orientation of electrons in the conduction band is caused by the indirect
scattering with virtual intermediate states in the valence band and allowance
for selection rules for interband transitions. The considered mechanism of
optical orientation is shown to be in an inherent relation with the special
Elliot-Yafet mechanism of electron spin relaxation induced by virtual interband
scattering.Comment: 3 pages, 2 figures, Symposium "Nanostructures: Physics and
Technology", St.Petersburg, Russia, 200
Lateral optical anisotropy of type-II interfaces in the tight-binding approach
We have developed the tight-binding theory to study electronic and optical
properties of type-II heterostructures CA/C'A' grown from the zinc-blende
semiconductors CA and C'A' along the crystallographic direction [001]. The
sp^3s* nearest-neighbor tight-binding model with allowance for the spin-orbit
interaction is used to calculate the energy states and the in-plane linear
polarization of the spatially-indirect band-edge photoluminescence of InAs/AlSb
and ZnSe/BeTe multi-layered structures. The interface parameters for a pair of
the nonstandard planes C-A' or C'-A are considered as fitting variables. A wide
range of these parameters are shown to allow Tamm-like hole states localized at
the interfaces. The theory leads to giant values of the light polarization in
the both type-II heterosystems in agreement with existing experimental
findings.Comment: 9 pages, 6 figures, submitted to Phys. Rev.
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