Angle evolution of the superconducting phase diagram in twisted bilayer WSe2

TL;DR

This study maps the evolution of superconducting phase diagrams in twisted bilayer WSe2 across various twist angles, revealing a smooth transition linked to Fermi surface reconstruction and establishing the material as a platform for studying correlated phases.

Contribution

It provides the first comprehensive experimental mapping of phase diagram evolution in twisted bilayer WSe2 across a range of twist angles, connecting previous distinct observations.

Findings

Superconducting state evolves smoothly with twist angle.

Proximal to Fermi surface reconstruction and possible antiferromagnetic order.

Not necessarily tied to Van Hove singularity or half band insulator.

Abstract

Recent observations of superconductivity in twisted bilayer WSe$_2$ have extended the family of moir\'e superconductors beyond twisted graphene. In WSe$_2$ two different twist angles were studied, 3.65{\deg} and 5.0{\deg}, and two seemingly distinct superconducting phase diagrams were reported, raising the question of whether the superconducting phases in the two devices share a similar origin. Here we address the question by experimentally mapping the evolution of the phase diagram across devices with twist angles spanning the range defined by the initial reports, and comparing the results to twist angle-dependent theory. We find that the superconducting state evolves smoothly with twist angle and at all twist angles is proximal to a Fermi surface reconstruction with, presumably, antiferromagnetic ordering, but is neither necessarily tied to the Van Hove singularity, nor to the half band insulator. Our results connect the previously distinct phase diagrams at 3.65{\deg} and 5{\deg}, and offer new insight into the origin of the superconductivity in this system and its evolution as the correlation strength increases. More broadly, the smooth phase diagram evolution, repeatability between different devices, and dynamic gate tunability within each device, establish twisted transition metal dichalcogenides as a unique platform for the study of correlated phases as the ratio of interaction strength to bandwidth is varied.