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

TL;DR

This study uses SQUID microscopy to investigate the current-phase relationship in Josephson junctions made from 3D topological insulator HgTe, revealing skewed CPRs indicative of high-transmittance Andreev bound states.

Contribution

It provides the first detailed characterization of the CPR in HgTe-based Josephson junctions, highlighting the role of helical Andreev bound states in the supercurrent.

Findings

Skewed current-phase relationships observed in HgTe junctions.

Persistence of skewness in junctions longer than the mean free path.

Indication of high-transmittance Andreev bound states contributing to supercurrent.

Abstract

We use Superconducting QUantum Interference Device (SQUID) microscopy to characterize the current-phase relation (CPR) of Josephson Junctions from 3-dimentional topological insulator HgTe (3D-HgTe). We find clear skewness in the CPRs of HgTe junctions ranging in length from 200 nm 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.