Moir´e flat bands and interfacial charge polarization in lattice relaxed twisted bilayer hexagonal boron nitride

We study the electronic structure and interfacial charge polarization of twisted bilayer hexagonal boron nitride (t2BN) as a function of twist angle and perpendicular electric fields. Our calculations rely on exact exchange and random phase approximation fitted force fields for the atomistic relaxations, and on first principles calculations informed intralayer and interlayer tight-binding hopping terms for the electronic structure. The sizeable interfacial charge polarization for h-BN bilayers near 0? parallel alignment can be understood from the maximal local interlayer dipoles forming at AB and BA stacking sites, while it is generally suppressed near 60? antiparallel alignment. Perpendicular electric fields modify the local interlayer distances and the local AB or BA stacking areas impacting the band gaps, band widths and local interlayer charge distributions associated with the nearly flat low energy bands.