High density electron doping in boron-doped twisted bilayer graphene: a ladder to extended flat-band

Abstract

Realizing Von Hove singularity (VHS) and extended flat bands of graphene near the Fermi level (E_F) is of great significance to explore many-body interactions, with a high tendency towards superconductivity. In this study, we report that the VHS of π* bands near E_F can be realized by high-density lithium intercalation in p-type doped twisted bilayer graphene (tBLG). First, a method to predict the highest lithium intercalation in tBLG systems with arbitrary twist angle was established which proves that the interlayer twisting leads to the clustering of lithium ions in the AA-region but reduces the overall concentration. Second, we show that the p-type doping (1.35% boron) in tBLGs enhances their electron acceptance capability by increasing lithium intercalation up to 47%. In this situation, the electron doping by lithium intercalation is sufficient to shift E_F near the VHS which offers a strategic path to realize extended flat bands, and to investigate the strong correlations in the tBLG systems.