Superconducting Diode Effect in Selectively-Grown Topological Insulator based Josephson Junctions

TL;DR

This study demonstrates a significant Josephson diode effect in topological insulator-based junctions, driven by spin-orbit coupling and magnetic fields, with potential for advanced superconducting device applications.

Contribution

It reports the observation of the Josephson diode effect in topological insulator Josephson junctions, highlighting the role of surface states and non-sinusoidal current-phase relationships.

Findings

Diode effect efficiency up to 7% under magnetic field

Presence of non-sinusoidal current-phase relationship

Anomalous phase shift attributed to surface states

Abstract

The Josephson diode effect, where the critical current magnitude depends on its direction, arises when both time-reversal and inversion symmetries are broken - often achieved by a combination of spin-orbit interaction and applied magnetic fields. Taking advantage of the strong spin-orbit coupling inherent in three-dimensional topological insulators, we study this phenomenon in Nb/Bi$_{0.8}$Sb$_{1.2}$Te$_3$/Nb Josephson weak-link junctions. Under an in-plane magnetic field perpendicular to the current direction, we observe a pronounced Josephson diode effect with efficiencies up to 7%. A crucial component of this behavior is the non-sinusoidal current-phase relationship and an anomalous phase shift, which we attribute to the presence of a ballistic supercurrent component due to the surface states. These findings open up new avenues for harnessing and controlling the Josephson diode effect in topological material systems.