Imaging Commensurate Minimally Twisted Bilayer Graphene Aligned to Hexagonal Boron Nitride*

Aligning magic-angle twisted bilayer graphene (TBG) with a hexagonal boron nitride (hBN)

substrate reveals the hidden non-trivial topology of the flat band through the appearance of a

quantum anomalous Hall effect (QAHE) in transport measurements. 1 The commensuration of the

two sets of Moiré patterns (graphene-graphene and graphene-hBN) is expected to occur, due to

the 1.8% difference in the lattice constants of graphene and hBN, only at a TBG twist angle of .

Surprisingly, by using low temperature scanning tunneling microscopy (STM) and spectroscopy

(STS), we find a locally stable commensurate double Moiré pattern for , suggesting strong

lattice relaxation effects that favor the alignment of the two Moiré patterns even for twist angles

that differ substantially from estimates based on rigid lattice calculations. We observe large

domains (200x200nm) of perfectly aligned double Moiré patterns separated by domain walls

where the built-up strain is released. Furthermore, STS reveals gaps at fractional fillings of the

flat band that increase in the presence of a magnetic field indicating that alignment with hBN

reveals an intrinsic non-trivial band topology even for twist angles far from the magic angle.