Synthesizing Coulombic superconductivity in van der Waals bilayers

Abstract

Synthesizing a polarizable environment surrounding a low-dimensional metal to generate superconductivity is a simple theoretical idea that still awaits a convincing experimental realization. The challenging requirements are satisfied in a metallic bilayer when the ratio between the Fermi velocities is small and both metals have a similar, low carrier density. In this case, the slower electron gas acts as a retarded polarizable medium (a “dielectric” environment) for the faster metal. Here we show that this concept is naturally optimized for the case of an atomically thin bilayer consisting of a Dirac semimetal (e.g., graphene) placed in atomic-scale proximity to a doped semiconducting transition metal dichalcogenide (e.g., WSe2). The superconducting transition temperature that arises from the dynamically screened Coulomb repulsion is computed using the linearized Eliashberg equation. In the case of graphene on WSe2, we find that Tc can exceed 100 mK, and it increases further when the Dirac valley degeneracy is reduced. Thus, we argue that suspended van der Waals bilayers are in a unique position to realize experimentally this long-anticipated theoretical concept.

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