Superconductivity and magnetic ordering in chalcogen-intercalated graphene bilayers with charge compensation

TL;DR

This paper explores a new class of 2D materials with graphene bilayers intercalated with chalcogen and alkaline earth layers, revealing potential for ferromagnetism and spin triplet superconductivity through theoretical electronic structure and interaction analysis.

Contribution

Introduces a novel AC8XC8 layered structure with detailed electronic and magnetic properties, highlighting coexistence of ferromagnetism and triplet superconductivity.

Findings

Complex Fermi surfaces with electron-hole compensation.

Proximity of van Hove singularities to Fermi level.

Dominant ferromagnetic instability and spin triplet pairing.

Abstract

This work introduces a new class of two-dimensional crystals with the structure AC$_8$XC$_8$, consisting of two layers of graphene, a chalcogen (X = O, S, Se, Te) intercalation layer, and an alkaline earth (A = Be, Ca, Mg, Sr, Ba) adlayer. The electronic band structure for the 20 compounds was studied using density functional theory. The chalcogen $p$ orbitals interact with the carbon $\pi$ orbitals to form weakly dispersing bands that give rise to complex Fermi surfaces featuring electron and hole pockets whose densities exactly compensate each other, and van Hove singularities that are very close to, or coincident with, the Fermi level in the majority of compounds studied. The resulting electron-electron interaction effects are studied using both the temperature-flow renormalisation group approach and a spin fluctuation model, which show a dominant ferromagnetic instability coexisting with $p$- or $f$-wave spin triplet superconductivity over a range of temperatures.