Band Engineering of Large-Twist-Angle Graphene/h−BN Moiré Superlattices with Pressure

Graphene interfacing hexagonal boron nitride ($h\text{\ensuremath{-}}\mathrm{BN}$) forms lateral moir\'e superlattices that host a wide range of new physical effects such as the creation of secondary Dirac points and band gap opening. A delicate control of the twist angle between the two layers is required as the effects weaken or disappear at large twist angles. In this Letter, we show that these effects can be reinstated in large-angle ($\ensuremath{\sim}1.8\ifmmode^\circ\else\textdegree\fi{}$) $\text{graphene}/h\text{\ensuremath{-}}\mathrm{BN}$ moir\'e superlattices under high pressures. A $\text{graphene}/h\text{\ensuremath{-}}\mathrm{BN}$ moir\'e superlattice microdevice is fabricated directly on the diamond culet of a diamond anvil cell, where pressure up to 8.3 GPa is applied. The band gap at the primary Dirac point is opened by 40--60 meV, and fingerprints of the second Dirac band gap are also observed in the valence band. Theoretical calculations confirm the band engineering with pressure in large-angle $\text{graphene}/h\text{\ensuremath{-}}\mathrm{BN}$ bilayers.