Superconductivity in topological Ψ-graphene

Abstract

Typical Dirac cones in graphene induce absence of electronic density around Fermi energy level (Ef), prohibiting intrinsic superconductivity. Here we probe to explore superior superconducting properties by involvements of pentagonal and heptagonal carbon rings into graphene. 5-7 polygons of metastable Ψ-graphene monolayer break hexagonal symmetry to bring type-II Dirac cones by band crossings. The polyhedral structure maintains integrity under high temperatures. Large specific surface area for Ψ-graphene monolayer expresses physical adsorption of NO molecule. Weak interactions of atomic bonding and antibonding features coexist with Bader charge transfer to carbon monolayer in close distance. The collective vibrations of carbon, nitrogen, and oxygen atoms deliver good dynamic stability of Ψ-graphene-NO adsorption system. In the Ψ-graphene, the shift of Dirac cones leads to the formation of visible Fermi surfaces, which motivates further investigation into their influences on the superconducting properties. Out-of-plane and in-plane carbon vibrations attribute to phonon modes in mediation with electron couplings. Based on computing the Eliashberg function, we evaluate strong electron-phonon coupling with the superconducting transition temperature reaching 22 K. These theoretical predictions can stimulate interests in exploring topological graphene allotropes of intrinsic superconductivity.