Wednesday, July 31, 2013

1307.7764 (Cihan Kurter et al.)

Evidence for an anomalous current-phase relation of a dc SQUID with
tunable topological junctions

Cihan Kurter, Aaron D. K. Finck, Yew San Hor, Dale J. Van Harlingen
Phase-sensitive measurements offer a promising route towards detection of gapless Majorana bound states (MBSs) that are predicted to exist in planar Josephson junctions (JJs) with 3D topological insulator barrier and characterized with an unusual current-phase relation (CPR). We search for the signatures of 4\pi-periodic component in CPR by studying a dc SQUID composed of two gate-tunable JJs with Bi2Se3 weak links incorporated into a superconducting Nb loop. This geometry reveals information about the CPR without being strongly affected by spatial inhomogeneity of the supercurrent that can distort the diffraction patterns of a single JJ. We observe unusual features in the magnetic field modulation of the SQUID critical current and in the magnetic diffraction patterns of the constituent single JJs that are consistent with a model incorporating a sin(\phi/2) component in the CPR that appears only when the phase difference across the junction is near an odd multiple of \pi.
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