Berlin 2012 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 9: Transport: Topological Insulators 1 (jointly with TT, MA)

HL 9.1: Talk

Monday, March 26, 2012, 09:30–09:45, H 3010

Quantum point contact as a probe of a topological superconductor — •Michael Wimmer, Anton Akhmerov, Jan Dahlhaus, and Carlo Beenakker — Instituut-Lorentz, Universiteit Leiden, The Netherlands

We calculate the conductance of a ballistic point contact to a superconducting wire, produced by the s-wave proximity effect in a semiconductor with spin-orbit coupling in a parallel magnetic field. The conductance G as a function of contact width or Fermi energy shows plateaus at half-integer multiples of 4e²/h if the superconductor is in a topologically nontrivial phase, supporting Majorana fermions. In contrast, the plateaus are at the usual integer multiples in the topologically trivial phase (without Majorana fermions). Disorder destroys all plateaus except the first, which remains precisely quantized, consistent with previous results for a tunnel contact. The advantage of a ballistic contact over a tunnel contact as a probe of the topological phase is the strongly reduced sensitivity to