Nonsinusoidal current-phase relationship in Josephson junctions from the 3D topological insulator HgTe

Ilya Sochnikov; Luis Maier; Christopher A Watson; John R Kirtley; Charles Gould; Grigory Tkachov; Ewelina M Hankiewicz; Christoph Brüne; Hartmut Buhmann; Laurens W Molenkamp; Kathryn A Moler

doi:10.1103/PhysRevLett.114.066801

Nonsinusoidal current-phase relationship in Josephson junctions from the 3D topological insulator HgTe

Phys Rev Lett. 2015 Feb 13;114(6):066801. doi: 10.1103/PhysRevLett.114.066801. Epub 2015 Feb 9.

Affiliations

¹ Department of Applied Physics, Stanford University, Stanford, California 94305, USA and Geballe Laboratory for Advanced Materials, Stanford University, Stanford, California 94305, USA.
² Physikalisches Institut (EP3), University of Würzburg, Am Hubland, 97074 Würzburg, Germany.
³ Department of Applied Physics, Stanford University, Stanford, California 94305, USA and Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.
⁴ Geballe Laboratory for Advanced Materials, Stanford University, Stanford, California 94305, USA and Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.
⁵ Institute for Theoretical Physics and Astrophysics, University of Würzburg, Am Hubland, 97074 Würzburg, Germany.
⁶ Department of Applied Physics, Stanford University, Stanford, California 94305, USA and Geballe Laboratory for Advanced Materials, Stanford University, Stanford, California 94305, USA and Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.

PMID: 25723235
DOI: 10.1103/PhysRevLett.114.066801

Abstract

We use superconducting quantum interference device microscopy to characterize the current-phase relation (CPR) of Josephson junctions from the three-dimensional topological insulator HgTe (3D HgTe). We find clear skewness in the CPRs of HgTe junctions ranging in length from 200 to 600 nm. The skewness indicates that the Josephson current is predominantly carried by Andreev bound states with high transmittance, and the fact that the skewness persists in junctions that are longer than the mean free path suggests that the effect may be related to the helical nature of the Andreev bound states in the surface of HgTe. These experimental results suggest that the topological properties of the normal state can be inherited by the induced superconducting state, and that 3D HgTe is a promising material for realizing the many exciting proposals that require a topological superconductor.