Quasiperiodic Moiré Reconstruction and Modulation of Electronic Properties in Twisted Bilayer Graphene Aligned with Hexagonal Boron Nitride.

Abstract

Twisted van der Waals systems have emerged as intriguing arenas for exploring exotic strongly correlated and topological physics, with structural reconstruction and strain playing essential roles in determining their electronic properties. In twisted bilayer graphene aligned with hexagonal boron nitride (TBG/h-BN), the interplay between the two sets of moiré patterns from graphene-graphene (G-G) and graphene-h-BN (G-h-BN) interfaces can trigger notable moiré pattern reconstruction (MPR). Here, we present the quasiperiodic MPR in the TBG/h-BN with two similar moiré wavelengths, wherein the MPR results from the incommensurate mismatch between the wavelengths of the G-G and G-h-BN moiré patterns. The short-range, nearly ordered moiré super-superstructures deviate from moiré quasicrystal and are accompanied by inhomogeneous strain, thereby inducing spatially variable energy separations between the Van Hove singularities (VHs) in the band structures of the TBG near the magic angle. By tuning the carrier densities in our sample, correlated gaps at specific AA sites are observed, uncovering the quantum-dot-like behavior and incoherent characteristics of the AA sites in the TBG. Our findings would give new hints on the microscopic mechanisms underlying the abundant novel quantum phases in the TBG/h-BN.