Dresden 2014 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 70: Transport: Topological Insulators II (organized by TT)

TT 70.7: Talk

Wednesday, April 2, 2014, 18:00–18:15, HSZ 204

Majorana fermions on a hexagonally warped 3D topological insulator in proximity to a superconductor — •Daniel Mendler, Panagiotis Kotetes, and Gerd Schön — Institut für theoretische Festkörperphysik, KIT, Karlsruhe

The recent discovery of topological insulators (TIs) opened new perspectives in the field of topological quantum computing (TQC), in terms of Majorana fermions (MFs). The latter are expected to appear in the vortex cores of artificial topological superconductors (TSCs), engineered from the surface states of a 3D-TI in proximity to a conventional SC. Nonetheless, if time-reversal symmetry is spontaneously broken on the TI surface, the hybrid system supports Majorana fermions without the requirement of vortices. The latter property can be advantageous for the experimental realization of TSCs and facilitate the implementation of TQC protocols. In this work, we investigate the above scenario for the hexagonally warped Dirac itinerant surface states of Bi2Te3, which demonstrate enhanced tendency towards the spontaneous formation of magnetism due to Fermi surface nesting. We perform a complete classification of the accessible spin density wave order parameters in the presence of a repulsive Hubbard-like interaction and retrieve the hierarchy of magnetic phase transitions which can occur in the particular system. For the dominant magnetic instability, we investigate the conditions which favor proximity induced SC on the magnetic TI surface. We explicitly demonstrate the emergence of MFs in this system and propose methods for their manipulation.