Flat bands without twists: periodic holey graphene

Abstract

\textit{Holey Graphene} (HG) is a widely used graphene material for the synthesis of high-purity and highly crystalline materials. In this work, we explore the electronic properties of a periodic distribution of lattice holes, demonstrating the emergence of flat bands with compact localized states. It is shown that the holes break the bipartite sublattice and inversion symmetries, inducing gaps and a nonzero Berry curvature. Moreover, the folding of the Dirac cones from the hexagonal Brillouin zone (BZ) to the holey superlattice rectangular BZ of HG with sizes proportional to an integer $n$ times the graphene's lattice parameter leads to a periodicity in the gap formation such that $n\equiv 0$ (mod $3$). Meanwhile, it is shown that if $n\equiv \pm 1$ (mod $3$), a gap emerges where Dirac points are folded along the $\Gamma -X$ path. The low-energy hamiltonian for the three central bands is also obtained, revealing that the system behaves as an effective $\alpha -{\mathcal{T}}_3$ graphene material. Therefore, a simple protocol is presented here that allows obtaining flat bands at will. Such bands are known to increase electron-electron correlated effects. This work provides an alternative system, much easier to build than twisted systems, to obtain highly correlated quantum phases.

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Cited by in corpus (3)

• Band structure and optical response of Kekulé-modulated $\alpha -{\mathcal{T}}_3$ model
• Topological Degeneracy Induced Flat Bands in two-Dimensional Holed Systems
• Generally covariant geometric momentum and geometric potential for a Dirac fermion on a two-dimensional hypersurface