Moiré flat bands and interfacial charge polarization in lattice relaxed twisted bilayer hexagonal boron nitride under perpendicular electric fields

Interfacial charge polarization of twisted bilayer hexagonal boron nitride (t2BN) is calculated as a function of twist angle and perpendicular electric fields through tight-binding calculations on lattice relaxed geometries, where the atomic and electronic structure models are informed by density functional theory input data from small unit cell simulations. We show that lattice relaxations tend to increase the bandwidth of the nearly flat bands, where bandwidths smaller than 0.01 eV are expected for θ ≲ 1.08◦ for BN/BN alignment near 0◦, and smaller than θ ≲ 1.5◦ for BN/NB alignment near 60◦. Local interfacial charge polarization maxima of ∼3 · 1012cm−2 expected for h-BN bilayers near 0◦ degrees at the AB and BA stacking sites tend to decrease with increasing twist angle, while the interlayer charge polarization is negligibly small for antiparallel alignment twists. Perpendicular electric fields are found to alter the AB and BA stacking areas and interlayer distances, giving rise to changes in the band gaps, the bandwidth of the nearly flat bands, and the local interlayer charge distributions.