Regensburg 2013 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 14: Topological Insulators 2 (jointly with DS, HL, MA, TT)
O 14.5: Vortrag
Montag, 11. März 2013, 16:30–16:45, H10
Dirac States in a Novel Topological Insulator: Epitaxial alpha-Tin Layers on Indium Antimonide — •J. Schäfer1, A. Barfuß1, G. Bihlmayer2, D. Wortmann2, L. Dudy1, P. Höpfner1, A. Bostwick3, E. Rotenberg3, and R. Claessen1 — 1Phys. Inst., Universität Würzburg, D — 2Peter Grünberg Inst. and Inst. Adv. Sim., FZ Jülich, D — 3Lawrence Berkeley Nat. Lab., USA
This study addresses a new material realization of a topological insulator (TI) thus far only proposed theoretically, which is formed by α-Sn in the diamond lattice on InSb substrates. The epitaxial growth opens various pathways to access and manipulate the topological surface state (TSS). This includes the evolution of the Dirac bands as a function of thickness, or surface coating layers which alter the spin-orbit interaction. Interestingly, the TI band properties are closely related to that of strained HgTe, for which the Quantum Spin Hall effect was demonstrated.
Here we report on the electronic structure of α-Sn(001) based on angle-resolved photoemission (ARPES), complemented by density functional theory (DFT). We observe the formation of a clearly pronounced Dirac cone. The Fermi level in ARPES is located close to the Dirac point. Its position can be controlled by dopants, which allows to adjust the Fermi level crossings of the TSS. The Dirac cone is discernible down to bulk band energies, and its constant energy surfaces seemingly reflect the lattice symmetry. The experimental findings are consistent with DFT calculations including spin-orbit interaction, which document the formation of a TSS.