Fig. 1: Twisted bilayer BN as a moiré polar substrate.
From: Moiré band structure engineering using a twisted boron nitride substrate
a Three high-symmetry stacking orders that exist in near-0°-twisted bilayer BN65. N and B atoms are shown in silver and green, respectively. In AA stacking (left), top and bottom atoms align right on top of each other, and there is no out-of-plane polarization. In AB (middle) and BA (right) stacking, the vertical alignment of N and B atoms creates an out-of-plane electric dipole, leading to downward (upward) polarization in AB (BA) stacking. b Schematic of twisted bilayer BN, where moiré patterns form with AB (downward polarization), BA (upward polarization), and AA local stacking arrangements65. c Device schematic for using twisted BN as a moiré polar substrate. Target layer sits on top of twisted bilayer BN, feeling its periodic moiré potential U. The target layer is encapsulated by a thick BN on top, and electrically gated with a metal top gate and a graphite bottom gate. d Electrostatic simulation of potential strength U imposed on bilayer graphene in the device structure shown in c, and the moiré wavelength a is taken to be 18.5 nm. e Band structure calculation of bilayer graphene under the electrostatic moiré potential in (d). Arrows mark the locations of density of state (DOS) minima in the conduction band and valence band due to band folding induced by the superlattice potential.
