In a standard Josephson junction the current is zero when the phase difference between the superconducting leads is zero. This condition is protected by parity and time-reversal symmetries. However, the combined presence of spin-orbit coupling and magnetic field breaks these symmetries and can lead to a finite supercurrent even when the phase difference is zero. This is the so called anomalous Josephson effect -- the hallmark effect of superconducting spintronics --and can be characterized by the corresponding anomalous phase shift (ϕ0). We report the observation of a tunable anomalous Josephson effect in InAs/Al Josephson junctions measured via a superconducting quantum interference device (SQUID). By gate controlling the density of InAs we are able to tune the spin-orbit coupling of the Josephson junction by more than one order of magnitude. This gives us the ability to tune ϕ0, and opens several new opportunities for superconducting spintronics, and new possibilities for realizing and characterizing topological superconductivity.
@article{arxiv.1905.12670,
title = {Gate Controlled Anomalous Phase Shift in Al/InAs Josephson Junctions},
author = {William Mayer and Matthieu C. Dartiailh and Joseph Yuan and Kaushini S. Wickramasinghe and Enrico Rossi and Javad Shabani},
journal= {arXiv preprint arXiv:1905.12670},
year = {2020}
}