Twist-programmable superconductivity in spin-orbit-coupled bilayer graphene.

Abstract

The relative twist angle between layers of near-lattice-matched van der Waals materials is critical for the emergent phenomena associated with moiré flat bands^1-3. However, the concept of angle rotation control is not exclusive to moiré superlattices in which electrons directly experience a twist-angle-dependent periodic potential. Instead, it can also be used to induce programmable symmetry-breaking perturbations with the goal of stabilizing desired correlated states. Here we experimentally demonstrate 'moiréless' twist-tuning of superconductivity together with other correlated orders in Bernal bilayer graphene proximitized by tungsten diselenide. The precise alignment between the two materials systematically controls the strength of induced Ising spin-orbit coupling (SOC), profoundly altering the phase diagram. As Ising SOC is increased, superconductivity onsets at a higher displacement field and features a higher critical temperature, reaching up to 0.5 K. Within the main superconducting dome and in the strong Ising SOC limit, we find an unusual phase transition characterized by a nematic redistribution of holes among trigonally warped Fermi pockets and enhanced resilience to in-plane magnetic fields. The superconducting behaviour is theoretically compatible with the prominent role of interband interactions between symmetry-breaking Fermi pockets. Moreover, we identify two additional superconducting regions, one of which descends from an inter-valley coherent normal state and shows a Pauli-limit violation ratio exceeding 40, among the highest for all known superconductors^4-7. Our results provide insights into ultraclean graphene superconductors and underscore the potential of utilizing moiréless-twist engineering across a wide range of van der Waals heterostructures.