Gate‐Defined Josephson Weak‐Links in Monolayer WTe₂

Abstract

Systems combining superconductors with topological insulators offer a platform for the study of Majorana bound states and a possible route to realize fault tolerant topological quantum computation. Among the systems being considered in this field, monolayers of tungsten ditelluride (WTe2) have a rare combination of properties. Notably, it has been demonstrated to be a quantum spin Hall insulator (QSHI) and can easily be gated into a superconducting state. Measurements on gate‐defined Josephson weak‐link devices fabricated using monolayer WTe2 are reported. It is found that consideration of the 2D superconducting leads are critical in the interpretation of magnetic interference in the resulting junctions. The reported fabrication procedures suggest a facile way to produce further devices from this technically challenging material and the results mark the first step toward realizing versatile all‐in‐one topological Josephson weak‐links using monolayer WTe2.

Helicity-Sensitive Terahertz Detection in Monolayer 1T′-WTe2

“…Bulk 1T′-WTe 2 was recently demonstrated to be a type II Weyl semimetal exhibiting extreme nonsaturating magnetoresistance and room temperature ferroelectricity. − Meanwhile, high-temperature quantum spin Hall (QSH) states and gate-tunable superconductivity were observed in monolayer 1T′-WTe 2 attributed to its nontrivial spin-resolved Berry curvature properties. , The spin–orbit coupling in monolayer 1T′-WTe 2 induces an inverted, indirect tunable QSH gap near the Q and Q ′ valleys in momentum space. As a result, optical excitation of the QSH gap with mid-infrared circularly polarized laser was proposed and demonstrated to exhibit in-plane circular photogalvanic currents. , The QSH gap of monolayer 1T′-WTe 2 is calculated to be around 30 meV by density functional theory (DFT) with the generalized gradient approximation method, indicating that long-wavelength THz excitation would be more suitable for studying the QSH states and valley-dependent transitions. Valley polarization has been created in conventional TMDCs using excitation by circularly polarized light and has been detected both electrically and optically, reversely indicating great potential in helicity-sensitive photodetectors utilizing these internal degrees of freedom of valleys .…”