18 research outputs found
Electron Spin Dynamics in Semiconductors without Inversion Symmetry
We present a microscopic analysis of electron spin dynamics in the presence
of an external magnetic field for non-centrosymmetric semiconductors in which
the D'yakonov-Perel' spin-orbit interaction is the dominant spin relaxation
mechanism. We implement a fully microscopic two-step calculation, in which the
relaxation of orbital motion due to electron-bath coupling is the first step
and spin relaxation due to spin-orbit coupling is the second step. On this
basis, we derive a set of Bloch equations for spin with the relaxation times
T_1 and T_2 obtained microscopically. We show that in bulk semiconductors
without magnetic field, T_1 = T_2, whereas for a quantum well with a magnetic
field applied along the growth direction T_1 = T_2/2 for any magnetic field
strength.Comment: to appear in Proceedings of Mesoscopic Superconductivity and
Spintronics (MS+S2002
Kinetics of proton pumping in cytochrome c oxidase
We propose a simple model of cytochrome c oxidase, including four redox
centers and four protonable sites, to study the time evolution of
electrostatically coupled electron and proton transfers initiated by the
injection of a single electron into the enzyme. We derive a system of master
equations for electron and proton state probabilities and show that an
efficient pumping of protons across the membrane can be obtained for a
reasonable set of parameters. All four experimentally observed kinetic phases
appear naturally from our model. We also calculate the dependence of the
pumping efficiency on the transmembrane voltage at different temperatures and
discuss a possible mechanism of the redox-driven proton translocation.Comment: 32 pages, 4 figures; references added. Minor changes in the
Acknowledgements sectio
Electron Spin Relaxation in a Semiconductor Quantum Well
A fully microscopic theory of electron spin relaxation by the
D'yakonov-Perel' type spin-orbit coupling is developed for a semiconductor
quantum well with a magnetic field applied in the growth direction of the well.
We derive the Bloch equations for an electron spin in the well and define
microscopic expressions for the spin relaxation times. The dependencies of the
electron spin relaxation rate on the lowest quantum well subband energy,
magnetic field and temperature are analyzed.Comment: Revised version as will appear in Physical Review
Negative high-frequency differential conductivity in semiconductor superlattices
We examine the high-frequency differential conductivity response properties
of semiconductor superlattices having various miniband dispersion laws. Our
analysis shows that the anharmonicity of Bloch oscillations (beyond
tight-binding approximation) leads to the occurrence of negative high-frequency
differential conductivity at frequency multiples of the Bloch frequency. This
effect can arise even in regions of positive static differential conductivity.
The influence of strong electron scattering by optic phonons is analyzed. We
propose an optimal superlattice miniband dispersion law to achieve
high-frequency field amplification
Self-induced and induced transparencies of two-dimensional and three- dimensional superlattices
The phenomenon of transparency in two-dimensional and three-dimensional
superlattices is analyzed on the basis of the Boltzmann equation with a
collision term encompassing three distinct scattering mechanisms (elastic,
inelastic and electron-electron) in terms of three corresponding distinct
relaxation times. On this basis, we show that electron heating in the plane
perpendicular to the current direction drastically changes the conditions for
the occurrence of self-induced transparency in the superlattice. In particular,
it leads to an additional modulation of the current amplitudes excited by an
applied biharmonic electric field with harmonic components polarized in
orthogonal directions. Furthermore, we show that self-induced transparency and
dynamic localization are different phenomena with different physical origins,
displaced in time from each other, and, in general, they arise at different
electric fields.Comment: to appear in Physical Review