Lateral Josephson effect on the surface of Co$_3$Sn$_2$S$_2$ magnetic Weyl semimetal

TL;DR

This study demonstrates long-range Josephson effects on the surface of magnetic Weyl semimetal Co$_3$Sn$_2$S$_2$, likely due to topologically protected surface states facilitating spin-triplet pairing, with implications for topological superconductivity.

Contribution

First experimental observation of Josephson current over 5 micrometers on a magnetic Weyl semimetal surface, suggesting topological surface states enable long-range superconducting proximity effects.

Findings

Josephson current observed over 5 μm junctions.

Unusual magnetic field and temperature dependencies of the Josephson effect.

Proposed contribution of Fermi-arc states to spin-triplet pairing.

Abstract

We experimentally study lateral electron transport between two 5~$\mu$m spaced superconducting indium leads on a top of magnetic Weyl semimetal Co$_3$Sn$_2$S$_2$. For the disordered magnetic state of Co$_3$Sn$_2$S$_2$ crystal, we only observe the Andreev reflection in the proximity of each of the leads, which is indicative of highly transparent In-Co$_3$Sn$_2$S$_2$ interfaces. If the sample is homogeneously magnetized, it demonstrates well-developed anomalous Hall effect state. In this regime we find the Josephson current that takes place even for 5~$\mu$m long junctions and shows the unusual magnetic field and temperature dependencies. As a possible reason for the results obtained, we discuss the contribution to the proximity-induced spin-triplet Josephson current from the topologically protected Fermi-arc states on the surface of Co$_3$Sn$_2$S$_2$.