Enhanced superconductivity in spin-orbit proximitized bilayer graphene.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Materials

Background:

• Bernal-stacked bilayer graphene (BLG) exhibits broken-symmetry metallic phases and fragile superconductivity under electric fields.
• Existing superconducting states in BLG are limited by narrow density ranges and low critical temperatures (Tc ≈ 30mK).

Purpose of the Study:

• To investigate the effect of monolayer tungsten diselenide (WSe2) on the superconducting properties of BLG.
• To explore methods for enhancing superconductivity in graphene-based systems.

Main Methods:

• Fabrication of BLG-WSe2 heterostructures.
• Measurement of quantum oscillations as a function of electric field and doping.
• In-plane magnetic field measurements to probe critical field dependence.

Main Results:

• Superconductivity in BLG-WSe2 appears at zero magnetic field with an order of magnitude higher Tc and an eightfold wider density range.
• Superconductivity emerges in a polarized normal state with two populated spin-valley flavors.
• Critical field dependence on doping shows deviations from the Chandrasekhar-Clogston limit.
• Superconductivity is stabilized by proximity-induced Ising spin-orbit coupling from WSe2.

Conclusions:

• Integrating WSe2 significantly enhances and stabilizes superconductivity in BLG.
• Proximity-induced spin-orbit coupling is crucial for robust Cooper pairing in this system.
• This work enables the engineering of tunable, ultra-clean graphene-based superconductors.