Dirac Fermion Cloning, Moir$\bf{\'e}$ Flat Bands and Magic Lattice Constants in Epitaxial Monolayer Graphene

TL;DR

This paper demonstrates that substrate-induced periodic modulation in epitaxial monolayer graphene can clone Dirac fermions, leading to flat band formation at specific lattice constants, opening pathways for exploring novel quantum phases.

Contribution

It introduces a new method to realize flat bands in monolayer graphene via substrate modulation, distinct from multilayer coupling approaches.

Findings

Substrate modulation causes Dirac fermion cloning in monolayer graphene.

Flat bands emerge at specific 'magic' lattice constants.

Experimental and theoretical results support the cloning and flat band formation.

Abstract

Tuning interactions between Dirac states in graphene has attracted enormous interest because it can modify the electronic spectrum of the two-dimensional material, enhance electron correlations, and give rise to novel condensed-matter phases such as superconductors, Mott insulators, Wigner crystals and quantum anomalous Hall insulators. Previous works predominantly focus on the flat band dispersion of coupled Dirac states from different graphene layers. In this work, we propose a new route to realizing flat band physics in monolayer graphene under a periodic modulation from substrates. We take gaphene/SiC heterostructure as a role model and demonstrate experimentally the substrate modulation leads to Dirac fermion cloning and consequently, the proximity of the two Dirac cones of monolayer graphene in momentum space. Our theoretical modeling captures the cloning mechanism of Dirac states and indicates that flat bands can emerge at certain magic lattice constants of substrate when the period of modulation becomes nearly commensurate with the $(\sqrt{3}\times\sqrt{3})R30^{\circ}$ supercell of graphene. The results show that the epitaxial monolayer graphene is a promising platform for exploring exotic many-body quantum phases arising from interactions between Dirac electrons.