Berlin 2018 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 50: HL Poster IV

HL 50.21: Poster

Thursday, March 15, 2018, 19:00–21:00, Poster B

MBE grown ultrathin and magnetically doped topological insulator films — •Andrea Bliesener¹, Gertjan Lippertz^1,2, Fan Yang¹, Alexey Taskin¹, and Yoichi Ando¹ — ¹Institute of Physics II, University of Cologne, Germany — ²Instituut voor Kern- en Stralingsfysica, KU Leuven, Belgium

Topological insulators (TIs) belong to a new class of quantum materials in which a strong spin-orbit coupling leads to a band inversion and, as a consequence, to a symmetry-protected gapless metallic state on the surface. Time-reversal symmetry breaking by magnetic doping opens a energy gap at the Dirac point. This kind of gapped topological insulator has been reported to show new quantum phenomena, including the quantum anomalous Hall effect (QAHE).

To observe these kind of novel quantum phenomena, fabrications of thin-film devices are required which allows for tuning the Fermi level across the Dirac point. It is necessary to improve growth conditions for the ternary compound (Bi_1−xSb_x)₂Te₃ such that the composition between n-type Bi₂Te₃ and p-type Sb₂Te₃ can be almost perfectly compensated. Decreasing the thickness of the MBE grown films, reduces the bulk-to-surface ratio and leads to TI samples where the surface transport is dominating. Doping ultrathin films with V or Cr allows to obtain the ferromagnetic state, which opens a gap in the surface states, leading to the QAHE at low temperatures.

In this contribution we report our efforts to grow ultrathin (Bi_1−xSb_x)₂Te₃ films and to increase the T_c of V-doped samples.