Zener Tunneling Between Landau Orbits in a High-Mobility Two-Dimensional Electron Gas

Magnetotransport in a laterally confined two-dimensional electron gas (2DEG) can exhibit modified scattering channels owing to a tilted Hall potential. Transitions of electrons between Landau levels with shifted guiding centers can be accomplished through a Zener tunneling mechanism, and make a significant contribution to the magnetoresistance. A remarkable oscillation effect in weak field magnetoresistance has been observed in high-mobility 2DEGs in GaAs-AlGa$_{0.3}$As$_{0.7}$ heterostructures, and can be well explained by the Zener mechanism.Comment: 5 pages, 4 figures. Text slightly shortened, figures resize

Anomalous thickness dependence of the Hall effect in ultrathin Pb layers on Si(111)

The magnetoconductive properties of ultrathin Pb films deposited on Si(111) are measured and compared with density-functional electronic band-structure calculations on two-dimensional, free-standing, 1 to 8 monolayers thick Pb(111) slabs. A description with free-standing slabs is possible because it turned out that the Hall coefficient is independent of the substrate and of the crystalline order in the film. We show that the oscillations in sign of the Hall coefficient observed as a function of film thickness can be explained directly from the thickness dependent variations of the electronic bandstructure at the Fermi energy.Comment: 4 pages incl. 3 figures, RevTeX, to appear in Phys. Rev.

Quasiparticle transport equation with collision delay. II. Microscopic Theory

For a system of non-interacting electrons scattered by neutral impurities, we derive a modified Boltzmann equation that includes quasiparticle and virial corrections. We start from quasiclassical transport equation for non-equilibrium Green's functions and apply limit of small scattering rates. Resulting transport equation for quasiparticles has gradient corrections to scattering integrals. These gradient corrections are rearranged into a form characteristic for virial corrections

DENSITÉ D'ÉTATS ÉLECTRONIQUES ET FLUCTUATIONS LOCALES DE CONCENTRATION DANS LES ALLIAGES BINAIRES DÉSORDONNÉS

Nous exposons une méthode améliorant les résultats de la théorie C. P. A. utilisée pour décrire les propriétés électroniques des alliages désordonnés. Nous définissons les notions de concentration locale et de potentiel cohérent local qui conduisent à l'obtention systématique des queues de bandes de densité d'états ignorées par la C. P. A. A titre d'illustration de la méthode, nous calculons la densité d'états d'un alliage binaire désordonné à une dimension et la comparaison est faite avec les résultats d'un calcul rigoureux et d'un calcul C. P. A.We present a method which improves the results of the C. P. A. theory, used to study electronic properties of disordered alloys. We define the notions of local concentration and local coherent potential which systematically yield tails in the allowed energy band. These tails cannot appear by C. P. A. calculations. As an illustration for our method, we calculate the electronic density of states of a simple one dimensional model and we compare it to exact density of states and to the results of the C. P. A