Induced superconductivity in the three-dimensional topological insulator HgTe

Luis Maier, Jeroen B. Oostinga, Daniel Knott, Christoph Bruene, Pauli Virtanen, Grigory Tkachov, Ewelina M. Hankiewicz, Charles Gould, Hartmut Buhmann, Laurens W. Molenkamp

Published 2012-10-16Version 1

A strained and undoped HgTe layer is a three-dimensional topological insulator, in which electronic transport occurs dominantly through its surface states. In this Letter, we present transport measurements on HgTe-based Josephson junctions with Nb as superconductor. Although the Nb-HgTe interfaces have a low transparency, we observe a strong zero-bias anomaly in the differential resistance measurements. This anomaly originates from proximity-induced superconductivity in the HgTe surface states. In the most transparent junction, we observe periodic oscillations of the differential resistance as function of an applied magnetic field, which correspond to a Fraunhofer-like pattern. This unambiguously shows that a precursor of the Josephson effect occurs in the topological surface states of HgTe.