Superconductivity in metallic twisted bilayer graphene stabilized by WSe₂

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Materials

Background:

• Magic-angle twisted bilayer graphene (TBG) exhibits diverse correlated electronic phases, including superconductivity.
• The emergence and relationship of these phases are sensitive to microscopic details and the dielectric environment.
• Superconductivity in TBG has been primarily observed near the magic angle (~1.1 degrees).

Purpose of the Study:

• To investigate the effect of incorporating a transition metal dichalcogenide (TMD) layer on the electronic properties of TBG.
• To stabilize superconductivity in TBG at twist angles significantly smaller than the magic angle.
• To explore the role of spin-orbit coupling in proximity-induced effects in TBG.

Main Methods:

• Fabrication of twisted bilayer graphene encapsulated with hexagonal boron nitride and a monolayer of tungsten diselenide (WSe2).
• Electrical transport measurements across a range of twist angles, electron densities, and magnetic fields.
• Analysis of signatures of superconductivity, weak antilocalization, and spin-valley symmetry breaking.

Main Results:

• Superconductivity is stabilized in TBG at twist angles as low as 0.79 degrees, well below the magic angle.
• Superconductivity is observed even when TBG exhibits metallic behavior across all electron densities.
• Evidence of weak antilocalization and broken spin-valley symmetry suggests proximity-induced spin-orbit coupling from WSe2.

Conclusions:

• The dielectric environment, specifically the presence of WSe2, plays a crucial role in stabilizing superconductivity in TBG.
• The findings provide constraints for theoretical models explaining superconductivity in TBG.
• This work opens new pathways for engineering quantum phenomena in moiré heterostructures.