Open AccessAtomistic Hartree theory of twisted double bilayer graphene near the magic angle
Author(s) -
Christopher T. S. Cheung,
Zachary A. H. Goodwin,
Valerio Vitale,
Johannes Lischner,
Arash A. Mostofi
Publication year - 2022
Publication title -
electronic structure
Language(s) - English
Resource type - Journals
ISSN - 2516-1075
DOI - 10.1088/2516-1075/ac5eaa
Subject(s) - bilayer graphene , hartree , ab initio , density functional theory , electronic structure , electron , graphene , ab initio quantum chemistry methods , condensed matter physics , molecular physics , electronic band structure , chemistry , materials science , atomic physics , physics , computational chemistry , nanotechnology , molecule , quantum mechanics
Twisted double bilayer graphene (tDBLG) is a moiré material that has recently generated significant interest because of the observation of correlated phases near the magic angle. We carry out atomistic Hartree theory calculations to study the role of electron–electron interactions in the normal state of tDBLG. In contrast to twisted bilayer graphene, we find that such interactions do not result in significant doping-dependent deformations of the electronic band structure of tDBLG. However, interactions play an important role for the electronic structure in the presence of a perpendicular electric field as they screen the external field. Finally, we analyze the contribution of the Hartree potential to the crystal field, i.e. the on-site energy difference between the inner and outer layers. We find that the on-site energy obtained from Hartree theory has the same sign, but a smaller magnitude compared to previous studies in which the on-site energy was determined by fitting tight-binding results to ab initio density-functional theory (DFT) band structures. To understand this quantitative difference, we analyze the ab initio Kohn–Sham potential obtained from DFT and find that a subtle interplay of electron–electron and electron–ion interactions determines the magnitude of the on-site potential.