Tunable coexisting moiré superlattices with rotatable van der Waals heterostructures

Nathan Finney
Columbia University

A long-wavelength geometric interference pattern, known as a moiré pattern, emerges in heterostructures of 2D materials featuring either a mismatch in lattice constants, an interlayer twist, or both. The scale and orientation of this moiré pattern can be controlled continuously via a sequence of mechanical pushes from an atomic force microscope (AFM) in contact mode. In this talk I will discuss recent experimental investigations of BN-encapsulated monolayer graphene, in which the bottom BN is persistently aligned to the graphene while the top BN can be rotated freely with an AFM. We observe equivalence under 120° rotations of top BN, with an enhancement of the graphene band gaps when the top and bottom BN are at 0° alignment, and a suppression of the gaps when the top BN is rotated by 60°. For small twist angles of the top BN we observe distinct secondary Dirac point features at high hole carrier density corresponding to the coexistence of multiple moiré potentials. By controlling the rotation at multiple interfaces and utilizing the symmetry of the crystals at each interface we can access a high degree of control and tunability in the properties of these layered systems.

Presentation (PowerPoint File)

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