Enhanced superconductivity in spin-orbit proximitized bilayer graphene

In the presence of a large perpendicular electric field, Bernal-stacked bilayer graphene (BLG) features several broken-symmetry metallic phases(1-3) as well as magnetic-field-induced superconductivity(1). The superconducting state is quite fragile, however, appearing only in a narrow window of density and with a maximum critical temperature T-c approximate to 30 mK. Here we show that placing monolayer tungsten diselenide (WSe2) on BLG promotes Cooper pairing to an extraordinary degree: superconductivity appears at zero magnetic field, exhibits an order of magnitude enhancement in T-c and occurs over a density range that is wider by a factor of eight. By mapping quantum oscillations in BLG-WSe2 as a function of electric field and doping, we establish that superconductivity emerges throughout a region for which the normal state is polarized, with two out of four spin-valley flavours predominantly populated. In-plane magnetic field measurements further reveal that superconductivity in BLG-WSe2 can exhibit striking dependence of the critical field on doping, with the Chandrasekhar-Clogston (Pauli) limit roughly obeyed on one end of the superconducting dome, yet sharply violated on the other. Moreover, the superconductivity arises only for perpendicular electric fields that push BLG hole wavefunctions towards WSe2, indicating that proximity-induced (Ising) spin-orbit coupling plays a key role in stabilizing the pairing. Our results pave the way for engineering robust, highly tunable and ultra-clean graphene-based superconductors.

Automated summary

A study finds that placing monolayer tungsten diselenide (WSe2) on bilayer graphene can enhance Cooper pairing and increase the critical temperature of superconductivity. The superconducting state exhibits polarized spin-valley flavors and occurs only under perpendicular electric fields that push graphene hole wavefunctions towards WSe2, indicating a key role of proximity-induced (Ising) spin-orbit coupling. These results pave the way for engineering robust, highly tunable, and ultra-clean graphene-based superconductors.