Berlin 2015 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 63: Topological Insulators: Theory (jointly with HL, DS, MA, O)
TT 63.4: Vortrag
Mittwoch, 18. März 2015, 10:15–10:30, ER 270
Effect of Bi bilayers on the topological states of Bi2Se3: A first-principles study — Kirsten Govaerts1, Kyungwha Park2, Christophe De Beule1, Dirk Lamoen1, and •Bart Partoens1 — 1CMT-group and EMAT, University of Antwerp, Belgium — 2Virginia Tech, Department of Physics, USA
Bi2Se3 and vice versa, has not been explored much. Bi bilayers are often present between the quintuple layers of Bi2Se3, since (Bi2)n(Bi2Se3)m form stable ground-state structures. Moreover, Bi2Se3 is a good substrate for growing ultrathin Bi bilayers. By first-principles techniques, we first show that there is no preferable surface termination by either Bi or Se. Next, we investigate the electronic structure of Bi bilayers on top of, or inside a Bi2Se3 slab. If the Bi bilayers are on top, we observe a charge transfer to the quintuple layers that increases the binding energy of the surface Dirac cones. The extra states, originating from the Bi bilayers, were declared to form a topological Dirac cone, but here we show that these are ordinary Rashba-split states. This result, together with the appearance of a new Dirac cone that is localized slightly deeper, might necessitate the reinterpretation of several experimental results. When the Bi bilayers are located inside the Bi2Se3 slab, they tend to split the slab into two topological insulators with clear surface states. Interface states can also be observed, but an energy gap persists because of strong coupling between the neighboring quintuple layers and the Bi bilayers.