Edge superconductivity in Multilayer WTe2 Josephson junction

TL;DR

This paper demonstrates edge superconductivity in multilayer WTe2 Josephson junctions, showing how supercurrent localization at edges depends on thickness, revealing potential for topological quantum phases.

Contribution

It provides direct experimental evidence of tunable edge superconductivity in multilayer WTe2, a topological material, using quantum interference measurements.

Findings

Supercurrent is bulk-dominated in thick WTe2 (~60 nm).

Supercurrent becomes edge-confined in thin WTe2 (10 nm).

Edge supercurrent width reaches up to 1.4 micrometers.

Abstract

WTe2, as a type-II Weyl semimetal, has 2D Fermi arcs on the (001) surface in the bulk and 1D helical edge states in its monolayer. These features have recently attracted wide attention in condensed matter physics. However, in the intermediate regime between the bulk and monolayer, the edge states have not been resolved owing to its closed band gap which makes the bulk states dominant. Here, we report the signatures of the edge superconductivity by superconducting quantum interference measurements in multilayer WTe2 Josephson junctions and we directly map the localized supercurrent. In thick WTe2 (~60 nm), the supercurrent is uniformly distributed by bulk states with symmetric Josephson effect ($\left|I_c^+(B)\right|=\left|I_c^-(B)\right|$). In thin WTe2 (10 nm), however, the supercurrent becomes confined to the edge and its width reaches up to 1.4 um and exhibits non-symmetric behavior $\left|I_c^+(B)\right|\neq \left|I_c^-(B)\right|$. The ability to tune the edge domination by changing thickness and the edge superconductivity establishes WTe2 as a promising topological system with exotic quantum phases and a rich physics.