Interplay of the volume and surface plasmons in the electron energy loss spectra of C60_{60}

The results of a joint experimental and theoretical investigation of the C60 collective excitations in the process of inelastic scattering of electrons are presented. The shape of the electron energy loss spectrum is observed to vary when the scattering angle increases. This variation arising due to the electron diffraction of the fullerene shell is described by a new theoretical model which treats the fullerene as a spherical shell of a finite width and accounts for the two modes of the surface plasmon and for the volume plasmon as well. It is shown that at small angles, the inelastic scattering cross section is determined mostly by the symmetric mode of the surface plasmon, while at larger angles, the contributions of the antisymmetric surface plasmon and the volume plasmon become prominent.Comment: 11 pages, 3 figure

Formalism for Multiphoton Plasmon Excitation in Jellium Clusters

We present a new formalism for the description of multiphoton plasmon excitation processes in jellium clusters. By using our method, we demonstrate that, in addition to dipole plasmon excitations, the multipole plasmons (quadrupole, octupole, etc) can be excited in a cluster by multiphoton absorption processes, which results in a significant difference between plasmon resonance profiles in the cross sections for multiphoton as compared to single-photon absorption. We calculate the cross sections for multiphoton absorption and analyse the balance between the surface and volume plasmon contributions to multipole plasmons.Comment: 29 pages, 1 figur

Ballistic side jump motion of electrons and holes in semiconductor quantum wells

We investigate the ballistic motion of electrons and holes in III-V semiconductor quantum wells with spin-orbit coupling and a homogeneous in-plane electric field. As a result of a non-perturbative treatment of both of these influences, particle wave packets undergo a pronounced side jump perpendicular to the field direction. For wave packets of sufficient width the amplitude of this motion can be estimated analytically and increases with decreasing field strength. We discuss the scaling behavior of the effect and some if its experimental implicationsComment: 4 pages, 3 figures include

Structure and properties of small sodium clusters

We have investigated structure and properties of small metal clusters using all-electron ab initio theoretical methods based on the Hartree-Fock approximation and density functional theory, perturbation theory and compared results of our calculations with the available experimental data and the results of other theoretical works. We have systematically calculated the optimized geometries of neutral and singly charged sodium clusters having up to 20 atoms, their multipole moments (dipole and quadrupole), static polarizabilities, binding energies per atom, ionization potentials and frequencies of normal vibration modes. Our calculations demonstrate the great role of many-electron correlations in the formation of electronic and ionic structure of small metal clusters and form a good basis for further detailed study of their dynamic properties, as well as structure and properties of other atomic cluster systems.Comment: 47 pages, 16 figure

Theoretical study of interacting hole gas in p-doped bulk III-V semiconductors

We study the homogeneous interacting hole gas in $p$-doped bulk III-V semiconductors. The structure of the valence band is modelled by Luttinger's Hamiltonian in the spherical approximation, giving rise to heavy and light hole dispersion branches, and the Coulomb repulsion is taken into account via a self-consistent Hartree-Fock treatment. As a nontrivial feature of the model, the self-consistent solutions of the Hartree-Fock equations can be found in an almost purely analytical fashion, which is not the case for other types of effective spin-orbit coupling terms. In particular, the Coulomb interaction renormalizes the Fermi wave numbers for heavy and light holes. As a consequence, the ground state energy found in the self-consistent Hartree-Fock approach and the result from lowest-order perturbation theory do not agree. We discuss the consequences of our observations for ferromagnetic semiconductors, and for the possible observation of the spin-Hall effect in bulk $p$-doped semiconductors. Finally, we also investigate elementary properties of the dielectric function in such systems.Comment: 9 pages, 5 figures, title slightly changed in the course of editorial process, a few references added, version to appear in Phys. Rev.

Spin Hall Effect

The intrinsic spin Hall effect in semiconductors has developed to a remarkably lively and rapidly growing branch of research in the field of semiconductor spintronics. In this article we give a pedagogical overview on both theoretical and experimental accomplishments and challenges. Emphasis is put on the the description of the intrinsic mechanisms of spin Hall transport in III-V zinc-blende semiconductors, and on the effects of dissipation.Comment: 22 pages, minor adjustments, version as publishe

Theory of spin-Hall transport of heavy holes in semiconductor quantum wells

Based on a proper definition of the spin current, we investigate the spin-Hall effect of heavy holes in narrow quantum wells in the presence of Rashba spin-orbit coupling by using a spin-density matrix approach. In contrast to previous results obtained on the basis of the conventional definition of the spin current, we arrive at the conclusion that an electric-field-induced steady-state spin-Hall current does not exist in both, pure and disordered infinite samples. Only an ac field can induce a spin-Hall effect in such systems.Comment: 6 pages, submitted to J. Phys.: Condens. Matte

Strain-Compensated AlInGaAs-GaAsP Superlattices for Highly-Polarized Electron Emission

Spin-polarized electron emission from the first superlattice photocathodes developed with strain compensation is investigated. An opposite strain in the quantum well and barrier layers is complished using an InAlGaAs/GaAsP superlattice structure. The measured values of maximum polarization and quantum yield for the structure with a 0.18 um-thick working layer are close to the best results reported for any strained superlattice photocathode structure, demonstrating the high potential of strain compensation for future photocathode applications. An analysis of the photoemission spectra is used to estimate the parameters responsible for the polarization losses.Comment: 10 pages, 2 figure

Optical Spin Orientation in Strained Superlattices

Optical orientation in the strained semiconductor superlattices is investigated theoretically. The dependence of the features in spin-polarization spectra on the structure parameters is clarified. The value of polarization in the first polarization maximum in the SL structures is shown to grow with the splitting between the hh- and lh- states of the valence band, the joint strain and confinement effects on the hh1- lh1 splitting being strongly influenced by the tunneling in the barriers. In strained structures with high barriers for the holes initial polarization can exceed 95 %. Calculated polarization spectra are close to the experimental spectra of polarized electron emission.Comment: 20 pages, 8 figure