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O: Fachverband Oberflächenphysik

O 29: Topological Insulators

O 29.1: Vortrag

Dienstag, 1. April 2014, 10:30–10:45, GER 38

Topological Insulator goes Elemental: α-Sn on InSb — •M. R. Scholz¹, A. Barfuss¹, L. Dudy¹, A. Fleszar², G. Bihlmayer³, D. Wortmann³, J. H. Dil⁴, G. Landolt⁴, M. Radovic⁴, G. Li², R. Claessen¹, and J. Schäfer¹ — ¹Phys. Inst. and RCCM, Univ. Würzburg — ²Inst. f. Theo. Physik u. Astronomie, Univ. Würzburg — ³Peter Grünberg Inst. a. Inst. f. Advanced Simulation, FZ Jülich — ⁴Swiss Light Source, Paul-Scherrer-Institut Villigen

We report on the topological insulator phase of epitaxially grown α-Sn on InSb substrates where compressive strain is induced by a slight lattice mismatch. The topological surface state (TSS) forms in the presence of an unusual band order not based on direct spin-orbit coupling, as shown in DFT and GW slab-layer calculations. Angle-resolved photoemission probes how the TSS emerges from the second highest bulk valence band. By means of spin-resolved photoemission we show that the surface state is highly spin-polarized with a counter-clockwise helicity below the Dirac point. The band situation in α-Sn closely resembles that of strained HgTe. Quantum well films of HgTe sandwiched between CdTe are a system where the topological properties have been successfully probed in DC transport [1]. The similarities to HgTe make α-Sn a promising candidate to exhibit the quantum spin Hall effect as well, if the film thickness is reduced to the 2D limit. Particularly, as a nontoxic elemental system, α-Sn is easier to fabricate which opens various pathways to access and manipulate the topological surface state. As a first step, we demonstrate the precise control of the Fermi level by dopants. [1] M. König et al., Science 318, 766 (2007).