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Register a new userAn extension of the optical Bloch equations: a microscopic approach including spin and carrier-phonon scattering
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This paper has been withdrawn by the authors. This is due to the fact that it has been substantially revised. As a consequence title and aim of the contents
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Semiconductor Bloch equations, in their extension including the spin degree of freedom of the carriers, are capable to describe spin dynamics on a microscopic level. In the presence of free holes, electron spins can flip simultaneously with hole spins due to electron-hole exchange interaction. This mechanism named after Bir, Aronov and Pikus, is described here by using the extended semiconductor Bloch equations and considering carrier-carrier interaction beyond the Hartree-Fock truncation. As a result we derive microscopic expressions for spin-relaxation and spin-dephasing rates.
We present an approach to spin dynamics by extending the optical Bloch equations for the driven two-level system to derive microscopic expressions for the transverse and longitudinal spin relaxation times. This is done for the 6-level system of electron and hole subband states in a semiconductor or a semiconductor quantum structure to account for the degrees-of-freedom of the carrier spin and the polarization of the exciting light and includes the scattering between carriers and lattice vibrations on a microscopic level. For the subsystem of the spin-split electron subbands we treat the electron-phonon interaction in second order and derive a set of equations of motion for the 2x2 spin-density matrix which describes the electron spin dynamics and contains microscopic expressions for the longitudinal (T_1) and the transverse (T_2) spin relaxation times. Their meaning will be discussed in relation to experimental investigations of these quantities.
Well-known Bloch equations describe the spin systems (electronic and nuclear) for any scale of time, from transient processes to steady states. Usually in solids T_2 << T_1. The question arises: what are the approximations that should be made in order the roughen Bloch equations to describe the processes at the time T_2 < t < T_1? The answer to this question is given in this article. As an example, the saturation of magnetic resonance is considered under the conditions of harmonic modulation of a constant magnetic field.
We construct a microscopic optical potential including breakup effects for elastic scattering of weakly-binding projectiles within the Glauber model, in which a nucleon-nucleus potential is derived by the $g$-matrix folding model. The derived microscopic optical potential is referred to as the eikonal potential. For $d$ scattering, the calculation with the eikonal potential reasonably reproduces the result with an exact calculation estimated by the continuum-discretized coupled-channels method. As the properties of the eikonal potential, the inaccuracy of the eikonal approximation used in the Glauber model is partially excluded. We also analyse the $^6$He scattering from $^{12}$C with the eikonal potential and show its applicability to the scattering with many-body projectiles.
The electronic structure of two V-based ladder compounds, the quarter-filled NaV$_2$O$_5$ in the symmetric phase and the iso-structural half-filled CaV$_2$O$_5$ is investigated by ab initio calculations. Based on the bandstructure we determine the dielectric tensor $epsilon(omega)$ of these systems in a wide energy range. The frequencies and eigenvectors of the fully symmetric A$_{g}$ phonon modes and the corresponding electron-phonon and spin-phonon coupling parameters are also calculated from first-principles. We determine the Raman scattering intensities of the A$_g$ phonon modes as a function of polarization and frequency of the exciting light. All results, i.e. shape and magnitude of the dielectric function, phonon frequencies and Raman intensities show very good agreement with available experimental data.
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