Berlin 2015 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 109: Transport: Majorana Fermions (jointly with DS, HL, MA, O)

TT 109.4: Vortrag

Freitag, 20. März 2015, 10:15–10:30, H 0104

Fractional Josephson Effect in HgTe based Josephson Junctions — •Jonas Wiedenmann1, Erwann Bocquillon1, Russel Deacon2, Simon Hartinger1, Luis Maier1, Christopher Ames1, Koji Ishibashi2, Tarucha Seigo3, Teun Klapwijk4, Hartmut Buhmann1, and Laurens Molenkamp11EP3, Physikalisches Institut, Universität Würzburg, Würzburg, Germany — 2Advanced Device Laboratory, RIKEN, Japan — 3Department of Applied Physics, Univeristy of Tokyo, Tokyo, Japan — 4Kavli Institute of Technology, Delft University of Technology, Delft, The Netherlands

3D topological insulators are a new class of material in which electronic transport is governed by topological surface states while the bulk remains insulating. Due to the helical spin polarization of the surface states, the coupling to a conventional s-wave superconductor is predicted to lead to the emergence of zero-energy bound states at the S-TI interface. These gapless zero energy states (sometimes referred to as Majorana bound states) are topologically protected against scattering and thus give rise to a 4π periodic Josephson current.

We fabricated Josephson junctions based on the three dimensional topological insulator HgTe and study its response under external rf excitation. An unconventional A.C. Josephson effect is observed which leads us to the conclusion that a 4π contribution in the Josephson current is present. In addition to the observation of an unconventional excess current, this gives robust signatures of the presence of zero-energy states.

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