Regensburg 2016 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 32: Transport: Topological Insulators - 3D
(Joint session of DS, HL, MA, O and TT organized by TT)

TT 32.6: Vortrag

Dienstag, 8. März 2016, 15:30–15:45, H18

Transport measurements on epitaxial Bi_1-xSb_x thin films grown on Si(111) — •Julian Koch, Philipp Kröger, Herbert Pfnür, and Christoph Tegenkamp — Leibniz Universität Hannover, Inst. für Festkörperphysik, Appelstr. 2, 30167 Hannover

The alloy Bi_1-xSb_x can be tuned to be either topologically trivial or non-trivial by changing the relative concentrations of Bismuth and Antimony [1]. In this study we present surface transport measurements performed on non-trivial Bi_1-xSb_x films. Thin films grown by in-situ co-deposition on Si(111) substrates are used, in order to reduce bulk contributions and to provide the possibility of nanostructuring. The morphology was controlled by low energy electron diffraction. Temperature dependent transport measurements for temperatures from 12 to 300 K were performed for films of different stoichiometry ranging from x=0.14−0.22 and thicknesses of 4, 8, 16 and 24 nm. We find strong evidence for metallic surface transport in addition to activated bulk transport, which is, to the best of our knowledge, the first observation of metallic surface transport in Bi_1-xSb_x films. In previous studies the transport findings were discussed solely in terms of impurity and bulk bands (see e.g. [2]). For films thinner than 6 nm the surface transport is strongly suppressed, in accordance with measurements on Bi₂Se₃ [3]. The temperature dependent transport behaviour of these films is similar to that of thicker films with substracted surface contribution as well as to films examined in previous studies, further supporting the observation of metallic surface transport in thicker films.

[1] H. Guo, K. Sugawara, A. Takayama, S. Souma, T. Sato, N. Satoh,

A. Ohnishi, M. Kitaura, M. Sasaki, Q.-K. Xue, and T. Takahashi,

PRB 83, 201104(R)

[2] S. Cho, A. DiVenere, G. K. Wong, J. B. Ketterson, and J. R. Meyer,

PRB 59 10691