Synthesizing Coulombic superconductivity in van der Waals bilayers

TL;DR

This paper proposes a new way to achieve superconductivity in van der Waals bilayers by using Coulombic interactions between a Dirac semimetal and a doped semiconductor, predicting transition temperatures over 100 mK.

Contribution

It introduces a theoretical framework for Coulombic superconductivity in atomically thin bilayers, specifically graphene on WSe₂, and predicts achievable transition temperatures.

Findings

Superconductivity can be induced by dynamically screened Coulomb repulsion.

Transition temperature $T_c$ can exceed 100 mK in graphene/WSe₂ bilayers.

Reducing Dirac valley degeneracy increases $T_c$.

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. WSe$_2$). 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 WSe$_2$, we find that $T_c$ 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.