Moiré flat bands and antiferroelectric domains in lattice relaxed twisted bilayer hexagonal boron nitride under perpendicular electric fields

Local interlayer charge polarization of twisted bilayer hexagonal boron nitride (t2BN) is calculated and parametrized as a function of twist angle and perpendicular electric fields through tight-binding calculations on lattice relaxed geometries lattice relaxations tend to increase the bandwidth of the nearly flat bands, where widths smaller than ∼1 meV are expected for θ≤1.08° for parallel BN/BN alignment, and for θ<1.5°, for the antiparallel BN/NB alignment. Local interlayer charge polarization maxima of ∼2.6 pC/m corresponding to interlayer electron density differences of ∼1.3×1012cm-2 are expected at the AB and BA stacking sites of BN/BN aligned t2BN in the long moire period limit for θ 1°, and evolves nonmonotonically with a maximum of ∼3.5 pC/m at θ=1.6° before reaching ∼2 pC/m for θ=6°. The electrostatic potential maxima due to the t2BN moiré patterns are overall enhanced by ∼20% with respect to the rigid system assuming potential modulation depths of up to ∼300 mV near its surface. In BN/BN aligned bilayers, the relative areas of the AB or BA local stacking regions can be expanded or reduced through a vertical electric field depending on its sign.