A metal-insulator transition by hole doping in boron triangular Kagome lattice

A flat band is the hallmark of a variety of exotic phases because electrons are confined in a narrow energy widnow with a very high density of states. Recently, much attention has been paid to magic-angle twisted bilayer graphene which possesses a flat band feature and exhibits strongly correlated and unconventional superconducting phases. This experiment indicates that partially-filled flat bands are the birthpalce of many intersesting phenomena and motivate further studies for the hidden physics of partially-filled flat bands in other systems. In this work, through first-principles calculations, we investigate the electronic structure and structural stability of a paritally-filled flat band in boron triangular Kagome lattice which has been recently predicted. We find that a large Fermi surface nesting in the partially-filled flat band enhances electron-phonon intearctions and induces dynamical instability. For hole doping levels above a 2/3-filling of the spin-polarized flat band, a metal-insulator transition occurs. Our results suggest that the boron triangular Kagome lattice is a suitable material to study the effect of partially-filled flat bands on exotic phases.