Electrically tunable low-density superconductivity in a monolayer topological insulator.

Fatemi, Valla; Wu, Sanfeng; Cao, Yuan; Bretheau, Landry; Gibson, Quinn D; Watanabe, Kenji; Taniguchi, Takashi; Cava, Robert J et al. · Science · 2018

basic_science · Level V

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Abstract

Turning on superconductivity in a topologically nontrivial insulator may provide a route to search for non-Abelian topological states. However, existing demonstrations of superconductor-insulator switches have involved only topologically trivial systems. Here we report reversible, in situ electrostatic on-off switching of superconductivity in the recently established quantum spin Hall insulator monolayer tungsten ditelluride (WTe<sub>2</sub>). Fabricated into a van der Waals field-effect transistor, the monolayer's ground state can be continuously gate-tuned from the topological insulating to the superconducting state, with critical temperatures <i>T</i> <sub>c</sub> up to ~1 kelvin. Our results establish monolayer WTe<sub>2</sub> as a material platform for engineering nanodevices that combine superconducting and topological phases of matter.