Regensburg 2013 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 21: Electronic Structure and Spin-Orbit Interaction I
O 21.10: Vortrag
Montag, 11. März 2013, 18:15–18:30, H42
Influence of adsorbates on the electronic structure of the topological insulator Bi2Se3: ab-initio investigations — •T. Förster1, P. Krüger1, M. Rohlfing1, A. Zumbülte2, C. Langenkämper2, A. B. Schmidt2, and M. Donath2 — 1Institut für Festkörpertheorie, Universität Münster, Germany — 2Physikalisches Institut, Universität Münster, Germany
Topological insulators possess helical surface states that are protected by time reversal symmetry. Additionally, traditional surface states exist. The rich physics of these systems is determined by the actual boundary conditions at the surface which can distinctly be affected by adatoms. Using density-functional calculations, we investigate the influence of adsorbates on the electronic structure of the Bi2Se3 surface. First, the effect of an adsorbate induced two-dimensional electron gas at the surface is studied by adding a respective long-ranged potential V(z) to the self-consistent one. This simple approach already leads to a down-shift of the Dirac point and the appearance of additional Rashba-like surface states similar to the findings of various experiments. In addition to this, we observe a W-shaped spin-split surface state in the unoccupied part of the band structure. This previously undescribed state is also seen in spin-resolved inverse-photoemission experiments. Secondly, our calculations show that monolayers of hydrogen or potassium adatoms give rise to long-ranged surface potentials and thus also induce the above mentioned features in the band structure. Furthermore, we find surface states that are specific to H and K, respectively.