Abstract
The quantum spin Hall insulator is characterized by a bandgap in the two-dimensional (2D) interior and helical 1D edge states1–3. Inducing superconductivity in the helical edge state results in a 1D topological superconductor, a highly sought-after state of matter at the core of many proposals for topological quantum computing4. In the present study, we report the coexistence of superconductivity and the quantum spin Hall edge state in a van der Waals heterostructure, by placing a monolayer of 1T′-WTe2, a quantum spin Hall insulator1–3, on a van der Waals superconductor, NbSe2. Using scanning tunnelling microscopy and spectroscopy (STM/STS), we demonstrate that the WTe2 monolayer exhibits a proximity-induced superconducting gap due to the underlying superconductor and that the spectroscopic features of the quantum spin Hall edge state remain intact. Taken together, these observations provide conclusive evidence for proximity-induced superconductivity in the quantum spin Hall edge state in WTe2, a crucial step towards realizing 1D topological superconductivity and Majorana bound states in this van der Waals material platform.
| Original language | English |
|---|---|
| Pages (from-to) | 526-530 |
| Number of pages | 5 |
| Journal | Nature Physics |
| Volume | 16 |
| Issue number | 5 |
| DOIs | |
| State | Published - May 1 2020 |
Funding
We thank D. Xiao, D. Cobden and X. Xu for helpful discussions and N. Speeney and N. Iskos for assistance in the laboratory. B.M.H. was supported by the Department of Energy under the Early Career award programme (DE-SC0018115). Crystal growth and characterization at ORNL were supported by the US Department of Energy, Office of Science, Basic Energy Sciences, Division of Materials Sciences and Engineering. We thank the Pennsylvania State University Two-Dimensional Crystal Consortium—Materials Innovation Platform (2DCC-MIP), which is supported by NSF DMR-1539916, for supplying further 2D materials. F.L. and D.W. were supported by the NSF DMR-1809145 for STM measurements. We acknowledge NSF DMR-1626099 for acquisition of the STM instrument. S.C.d.l.B. was supported by the Department of Energy (DE-SC0018115) for fabrication of proximity-effect van der Waals heterostructures. Density functional theory calculations were supported by the Department of Energy under grant no. DE-SC0014506.