Berlin 2018 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 99: Poster Session: Transport
TT 99.1: Poster
Donnerstag, 15. März 2018, 15:00–19:00, Poster B
Interface coupling in magnetoconductance of Bi-films on Si(111) — •Doaa Abdelbarey1, Philipp Kröger1, Christoph Tegenkamp1,2, and Herbert Pfnür1 — 1Inst. für Festkörperphysik, Leibniz Universität Hannover — 2Institut für Physik, TU Chemnitz
Bi ultrathin epitaxial films are governed by strongly spin-polarized bands that determine to a large extent their magnetotransport properties. Magneto conductance of films with a thickness of 20 to 60 bilayers on a Si(111) substrate was measured mostly at T = 11 K and in B-fields up to 4 T. The B-field orientation was varied from perpendicular to parallel to the surface. For the in-plane B-field orientation strong variations ofscattering properties between the interfaces were observed that depend both on the angle between B- and E-fields as well as on the film thickness. For the thinnest films, direct interaction between interfaces leads to strong spin depolarization and to a conductance almost independent of B. Thicker films exhibit a dominance of weak antilocalization, if B and E are parallel, but weak localization for both in plane, but perpendicular to each other. The latter contribution disappears at 100 K, where only WAL was seen. Since the potential gradients on both interfaces point in opposite directions normal to the surface, the spin directions in the same Rashba-split electronic bands are opposite (and in plane) for a given k||→. This means that only within the same layer backscattering is forbidden, since scattering from + k||→↑ to − k||→↓ requires spin Umklapp, but for scattering between the interfaces no Umklapp for the same process is necessary. Therefore, it is allowed.