Invited Paper MI-MoA6
Reorganization and Annihilation of Topologically Nontrivial Surface and Interface States

Monday, November 10, 2014, 3:40 pm, Room 311

Topological insulators are characterized by an insulating bulk and topologically protected surface states. The latter bridge the fundamental band gap und often show linear dispersion, i.e., a Dirac cone. In this presentation, I am going to answer two questions: how is the Dirac surface state of Bi₂Te₃ modified upon deposition of noble metal atoms? And second, is it possible to confine nontrivial interface states between two topological insulators? The findings have impact for spin-dependent transport.

The electronic structure of Au-covered Bi₂Te₃ is investigated by first-principles calculations [1]. The Dirac surface state of Bi₂Te₃ hybridizes with the Au sp states, which gives rise to strong reorganization of the surface electronic structure. Striking features of the modified Dirac surface state are (i) the introduction of new Dirac points within the fundamental band gap of Bi₂Te₃, (ii) an extremely weak dispersion, and (iii) an anisotropic number of conducting channels in the fundamental band gap of Bi₂Te₃ which leads to a complicated Fermi surface.

I shall also show that nontrivial electronic states exist at an interface of a Z₂ topological insulator and a topological crystalline insulator [2]. At the exemplary (111) interface between Bi₂Te₃ and SnTe, the two Dirac surface states at the Brillouin zone center annihilate upon approaching the semi-infinite subsystems but one topologically protected Dirac surface state remains at each time-reversal invariant momentum M. This leads to a highly conducting spin-momentum-locked channel at the interface but insulating bulk regions. For the Sb₂Te₃/Bi₂Te₃ interface, there is complete annihilation of Dirac states because both subsystems belong to the same topology class.

This work is supported by the Priority Program 1666 of DFG.

[1] Francisco Muñoz, Jürgen Henk, and Ingrid Mertig, submitted (2014).

[2] Tomáš Rauch, Markus Flieger, Jürgen Henk, and Ingrid Mertig, Phys. Rev. B 88 (2013) 245120.