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

FP Li and D Lee and N Leconte and S Javvaji and YD Kim and JL Jung, PHYSICAL REVIEW B, 110, 155419 (2024).

DOI: 10.1103/PhysRevB.110.155419

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 similar to 1 meV are expected for theta <= 1.08 degrees for parallel BN/BN alignment, and for theta <1.5 degrees, for the antiparallel BN/NB alignment. Local interlayer charge polarization maxima of similar to 2.6 pC/m corresponding to interlayer electron density differences of similar to 1.3x10(12) cm(-2) are expected at the AB and BA stacking sites of BN/BN aligned t2BN in the long moire period limit for theta << 1 degrees, and evolves nonmonotonically with a maximum of similar to 3.5 pC/m at theta=1.6 degrees before reaching similar to 2 pC/m for theta = 6 degrees. The electrostatic potential maxima due to the t2BN moire patterns are overall enhanced by similar to 20% with respect to the rigid system assuming potential modulation depths of up to similar 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.

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