Electrically Tunable Low Density Superconductivity in a Monolayer Topological Insulator

TL;DR

This paper demonstrates reversible electrical switching between topological insulating and superconducting states in monolayer WTe2, enabling new avenues for topological quantum devices and superconducting nanostructures.

Contribution

It reports the first in-situ electrostatic control of superconductivity in a monolayer topological insulator, WTe2, with low critical density and tunable critical temperature.

Findings

Superconductivity can be reversibly switched on and off in monolayer WTe2.

The critical temperature for superconductivity reaches up to ~1 Kelvin.

The critical carrier density for superconductivity is approximately 5 x 10^12 cm^-2.

Abstract

The capability to switch electrically between superconducting and insulating states of matter represents a novel paradigm in the state-of-the-art engineering of correlated electronic systems. An exciting possibility is to turn on superconductivity in a topologically non-trivial insulator, which provides a route to search for non-Abelian topological states. However, existing demonstrations of superconductor-insulator switches have involved only topologically trivial systems, and even those are rare due to the stringent requirement to tune the carrier density over a wide range. Here we report reversible, in-situ electrostatic on off switching of superconductivity in a recently established quantum spin Hall insulator, namely monolayer tungsten ditelluride (WTe2). 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 Tc up to ~ 1 Kelvin. The critical density for the onset of superconductivity is estimated to be ~ 5 x 10^12 cm^-2, among the lowest for two-dimensional (2D) superconductors. Our results establish monolayer WTe2 as a material platform for engineering novel superconducting nanodevices and topological phases of matter.