We assess the impact of atomistic substrate lattice relaxation schemes in the primary band gap at charge neutrality and the secondary valence band gap of graphene on hexagonal boron nitride (G/h-BN) as a function of twist angle. For zero twist angle, the primary gap decreases from ∼30~meV in fully relaxed suspended G/h-BN bilayers, to ∼9~meV when the remote h-BN substrate layer is kept rigid, and down to ∼3~meV in completely rigid structures. In the presence of relaxations, the primary gap shows a maximum near ∼0.6∘ coinciding with energetic stabilization due to alignment between the moir\'e pattern and the graphene lattice vectors, while the secondary valence band gap drops from ∼12~meV down to zero beyond twist angles of ∼1∘. A small but finite primary gap on the order of ∼1~meV, with a mass sign favoring electronic occupation of carbon atop boron, persists across twist angles from 0∘ to 30∘ for all sliding configurations, and switches sign for twist angles between 30∘ and 60∘.
@article{arxiv.2602.18893,
title = {Atomistic substrate relaxation effects in the band gaps of graphene on hexagonal boron nitride},
author = {Jiaqi An and Nicolas Leconte and Srivani Javvaji and Youngju Park and Jeil Jung},
journal= {arXiv preprint arXiv:2602.18893},
year = {2026}
}