Berlin 2015 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 66: Electronic Structure of Surfaces

O 66.12: Poster

Mittwoch, 18. März 2015, 18:15–21:00, Poster A

Tuning the Fermi energy to the Dirac point in the ternary topological insulator (Bi_1−xSb_x )₂Te₃ — •Jens Kellner¹, Markus Eschbach², Jörn Kampmeier³, Martin Lanius³, Gregor Mussler³, Lukasz Plucinski², Markus Liebmann¹, Detlev Grützmacher³, Claus Schneider², and Markus Morgenstern¹ — ¹II. Physikalisches Institut B, RWTH Aachen University and JARA-FIT, Germany — ²Forschungszentrum Jülich GmbH, Peter Grünberg Institut (PGI-6), Germany — ³Forschungszentrum Jülich GmbH, Peter Grünberg Institut (PGI-9), Germany

A topological insulator (TI) has a bulk energy gap but conducting helical surface states. In order to make use of these states, e.g. in transport devices or for creating exotic quasiparicles like Majorana Fermions, one has to tune the Fermi energy (E_F) close to the Dirac point (E_D) within the band gap. However, currently used TI materials e.g. Bi₂Te₃ and Sb₂Te₃ have major drawbacks. For Bi₂Te₃, E_D is buried in the bulk valence band (BVB) and E_F is located in the bulk conduction band (BCB). Whereas with Sb₂Te₃, E_D is in the bulk energy gap and E_F is located in the BVB. Mixing the two compounds leads to a ternary system (Bi_1−xSb_x)₂Te₃ where charge compensation is achieved and the position of E_D can be tuned [1].We were able to synthesize (Bi_1−xSb_x)₂Te₃ thin films for 0.94<x<0.96 by molecular beam epitaxy (MBE), transferred in-situ in ultrahigh vacuum from the MBE system to the photoemission setup. Angle resolved photoemission spectroscopy shows that E_F and E_D are congruent and no bulk bands intersect E_F. [1] J. Zhang, Nat. Comm. 2, 574 (2011)