Superconductivity in twisted bilayer WSe$_2$

TL;DR

This paper reports the first observation of superconductivity in twisted bilayer WSe₂, demonstrating that moiré flat-band superconductivity extends beyond graphene and can be influenced by unique TMD properties.

Contribution

The study provides the first experimental evidence of superconductivity in twisted bilayer WSe₂, expanding the scope of moiré flat-band superconductivity beyond graphene-based systems.

Findings

Superconductivity observed at 426 mK in twisted bilayer WSe₂.

Superconducting phase appears near a magnetic phase with Fermi surface reconstruction.

A sharp boundary between superconducting and magnetic phases suggests spin-fluctuation mediated pairing.

Abstract

The discovery of superconductivity in twisted bilayer and twisted trilayer graphene has generated tremendous interest. The key feature of these systems is an interplay between interlayer coupling and a moir\'e superlattice that gives rise to low-energy flat bands with strong correlations. Flat bands can also be induced by moir\'e patterns in lattice-mismatched and or twisted heterostructures of other two-dimensional materials such as transition metal dichalcogenides (TMDs). Although a wide range of correlated phenomenon have indeed been observed in the moir\'e TMDs, robust demonstration of superconductivity has remained absent. Here we report superconductivity in 5 degree twisted bilayer WSe$_2$ (tWSe$_2$) with a maximum critical temperature of 426 mK. The superconducting state appears in a limited region of displacement field and density that is adjacent to a metallic state with Fermi surface reconstruction believed to arise from antiferromagnetic order. A sharp boundary is observed between the superconducting and magnetic phases at low temperature, reminiscent of spin-fluctuation mediated superconductivity. Our results establish that moir\'e flat-band superconductivity extends beyond graphene structures. Material properties that are absent in graphene but intrinsic among the TMDs such as a native band gap, large spin-orbit coupling, spin-valley locking, and magnetism offer the possibility to access a broader superconducting parameter space than graphene-only structures.