Realization of a double-slit SQUID geometry by Fermi arc surface states in a WTe$_2$ Weyl semimetal

TL;DR

This study demonstrates long-range Josephson currents in WTe2, a Weyl semimetal with Fermi arc surface states, using a double-slit SQUID geometry to confirm topological surface state conduction.

Contribution

The paper reports the first realization of a double-slit SQUID geometry in WTe2, confirming the role of Fermi arc surface states in mediating Josephson currents over long distances.

Findings

Josephson current observed over 5 μm in WTe2 junctions.

Topological surface states carry the Josephson current.

Double-slit SQUID confirms surface state contribution.

Abstract

We experimentally study electron transport between two superconducting indium leads, coupled to the WTe$_2$ crystal surface. WTe$_2$ is characterized by presence of Fermi arc surface states, as a predicted type-II Weyl semimetal candidate. We demonstrate Josephson current in unprecedentedly long 5~$\mu$m In-WTe$_2$-In junctions, which is confirmed by $I-V$ curves evolution with temperature and magnetic field. The Josephson current is mostly carried by the topological surface states, which we demonstrate in a double-slit SQUID geometry, realized by coupling the opposite WTe$_2$ crystal surfaces.