Creating a custom-designed moiré magnifying glass to probe local atomic lattice rotations in twisted bilayer graphene

Moire materials have risen to the forefront of physics research because of their ability to realize a disparate set of fascinating physical phenomena in these systems. Besides interesting electronic properties, the moire pattern has been suggested to be used as a magnifying glass for local strain and dislocations in van der Waals (vdW) systems. Here, we demonstrate the ability to create a custom-designed moire magnifying glass to probe local atomic lattice rotations directly in tiny-angle twisted bilayer graphene (TBG). In tiny-angle TBG, a moire periodic network of local subdegree lattice rotations, i.e., the structural reconstruction, occurs due to the vdW interlayer interaction. By introducing a small-period graphene moire pattern as the magnifying glass, the local subdegree lattice rotations in the underlying tiny-angle TBG are magnified both in structure, i.e., the local moire periods, and in electronic properties, i.e., energy separations between two low-energy van Hove singularities. Our results unveil the unique magnifying effects of the moire pattern, and the reported method can be applied to probe the structural reconstruction in any vdW system.