Giant Splitting of Folded Dirac Bands in Kekul\'{e}-ordered Graphene with Eu Intercalation

Abstract

Kekul\'{e}-ordered graphene on SiC realized by intercalating two-dimensional metal layers offers a versatile platform for exploring intriguing quantum states and phenomena. Here, we achieve the intercalation of $(\mathrm{\sqrt{3}\times\sqrt{3}})\mathit{R}30^\circ$-ordered Eu layer between epitaxial graphene and SiC substrate, realizing a Kekul\'{e} graphene with large local magnetic moments of intercalated Eu atoms. Combining angle-resolved photoemission spectroscopy (ARPES) and density functional theory (DFT) calculations, we revealed that the Kekul{\'{e}} order folds the Dirac cones of graphene from the corners to the Brillouin zone center via intervalley scattering, forming the replica Dirac bands with gap opening. More intriguingly, the Dirac fermions in the replica Dirac bands show a strong exchange coupling with the localized magnetic moments of Eu $4f$ orbitals, resulting in a giant splitting of the folded Dirac bands. The observation of strong coupling between Dirac fermions and local magnetic moments of Eu $4f$ electrons via Kekul\'{e} order pave a new way for generating Dirac band splitting in graphene, advancing the potential applications of Kekul\'{e}-ordered graphene in spintronics, as well as exploring intriguing physical properties and correlation states for quantum technology.