Argonne National Laboratory

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Anomalous Josephson Current in Superconductor Topological Insulator Devices

Materials Science Seminar
Cihan Kurter, University of Illinois at Urbana-Champaign
April 2, 2014 2:00PM to 3:00PM
Building 223, Room S105
Josephson junctions (JJs) with topological insulator weak links are expected to host low-energy Andreev bound states (ABSs) giving rise to a current-phase relation that sharply deviates from a conventional sinusoidal behavior. Of particular interest are zero-energy Majorana bound states that form either at a vortex or when a phase difference of is imposed between the two closely-spaced superconducting leads of the junction.

In this talk, I will present signatures of an anomalous super current carried by topologically non-trivial ABSs in various superconducting quantum interference devices (SQUIDs) made of Nb BiSe Nb junctions. An electrostatic top gate placed on the JJs allows strong modulation of the Josephson current and the realization of a topological phase transition. I will discuss the possible mechanisms including the presence of a Majorana mode which could lead to qualitative modifications in the SQUID oscillations and single-junction diffraction patterns.