Josephson supercurrent through the topological surface states of strained bulk HgTe

TL;DR

This study demonstrates supercurrent flow through topological surface states of strained bulk HgTe in Josephson junctions, providing insights into Majorana states and the Josephson effect in topological insulators.

Contribution

It presents experimental evidence of supercurrent and Josephson effects in strained HgTe topological insulator surface states, advancing understanding of Majorana states.

Findings

Dissipationless supercurrent observed through surface states.

Hysteretic current-voltage characteristics below 1 K.

Fraunhofer pattern indicating 2π-periodic Josephson effect.

Abstract

Strained bulk HgTe is a three-dimensional topological insulator, whose surface electrons have a high mobility (30,000 cm^2/Vs), while its bulk is effectively free of mobile charge carriers. These properties enable a study of transport through its unconventional surface states without being hindered by a parallel bulk conductance. Here, we show transport experiments on HgTe-based Josephson junctions to investigate the appearance of the predicted Majorana states at the interface between a topological insulator and a superconductor. Interestingly, we observe a dissipationless supercurrent flow through the topological surface states of HgTe. The current-voltage characteristics are hysteretic at temperatures below 1 K with critical supercurrents of several microamperes. Moreover, we observe a magnetic field induced Fraunhofer pattern of the critical supercurrent, indicating a dominant 2\pi-periodic Josephson effect in the unconventional surface states. Our results show that strained bulk HgTe is a promising material system to get a better understanding of the Josephson effect in topological surface states, and to search for the manifestation of zero-energy Majorana states in transport experiments.