Berlin 2018 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 99: Poster Session: Transport

TT 99.2: Poster

Donnerstag, 15. März 2018, 15:00–19:00, Poster B

Controlling conductivity by quantum well states: ultrathin Bi(111) films. — Philipp Kröger¹, Doaa Abdelbarey¹, •Marvin Detert¹, Herbert Pfnür¹, and Christoph Tegenkamp^1,2 — ¹Institut für Festkörperphysik, Leibniz Universität Hannover — ²Institut für Physik, Technische Universität Chemnitz

Epitaxial Bi(111) films were subject to many and partly even controversial studies on the semimetal-semiconductor transition (SMSC) triggered by a robust quantum confinement. The remaining conductance was ascribed to conducting surface channels. We investigated ultra-thin crystalline Bi films on Si(111) as a function of film thickness between 20 and 100 bi-layers by means of electric transport measurements. Varying temperature and magnetic field, we disentangled essentially two transport channels. One remains indeed metallic at all thicknesses investigated with a slightly increasing conductance as a function of film thickness, d, whereas the second is activated with a d⁻¹-dependence of the activation energy, indicating a quasi-harmonic confining potential. Both channels reflect the properties of the whole quantized film and a strict separation into surface and bulk states, valid for electronic screening lengths much smaller than d, seems to be doubtful in these strongly quantum confined ultra-thin films. The metallic channel through the coupled edge states seems to be robust.