Dresden 2017 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 33: Transport: Majorana Fermions
TT 33.2: Talk
Tuesday, March 21, 2017, 14:15–14:30, HSZ 204
Gapless Andreev Bound States in HgTe based topological Josephson junctions — •Jonas Wiedenmann1, Erwann Bocquillon1, Russel Deacon2, Teun Klapwijk3, Philipp Leubner1, Christoph Brüne1, Seigo Tarucha2, Koji Ishibashi2, Hartmut Buhmann1, and Laurens Molenkamp1 — 1Physikalisches Institut 3, Am Hubland, Universität Würzburg — 2Advanced Device Laboratory, Riken, Japan — 3Kavli Institute of Nanoscience, Delf, The Netherlands
Due to their inverted bandstructure, HgTe quantum wells of appropriate thickness are a 2D TI and exhibit the Quantum Spin Hall effect. Such a topological insulator in proximity with a conventional superconductor is predicted to lead to the emergence of induced p-wave superconductivity. Majorana bound states occur as zero energy states in vortices or at edges of such a triplet pairing superconductors. In this talk I will focus on detecting two experimental signatures of such zero energy states. We show from the ac Josephson effect that the supercurrent across such a Josephson junction made of a HgTe based topological insulator, varies 4π periodically with the superconducting phase difference. Namely we identify a doubling of the Shapiro steps compared to conventional superconductors [1] and measure Josephson emission at half the Josephson frequency [2]. Furthermore, by applying a magnetic flux to the junction, we are able show that the supercurrent is predominantly carried by states edge states.
[1] Bocquillon et al. Nat. Nano (2016)
[2] Deacon et al. arXiv:1603.09611