Kavli Affiliate: Michael Crommie
| First 5 Authors: Kyunghoon Lee, M. Iqbal Bakti Utama, Salman Kahn, Appalakondaiah Samudrala, Nicolas Leconte
| Summary:
Two-dimensional heterostructures with layers of slightly different lattice
vectors exhibit a new periodic structure known as moire lattices. Moire lattice
formation provides a powerful new way to engineer the electronic structure of
two-dimensional materials for realizing novel correlated and topological
phenomena. In addition, superstructures of moire lattices can emerge from
multiple misaligned lattice vectors or inhomogeneous strain distribution, which
offers an extra degree of freedom in the electronic band structure design.
High-resolution imaging of the moire lattices and superstructures is critical
for quantitative understanding of emerging moire physics. Here we report the
nanoscale imaging of moire lattices and superstructures in various
graphene-based samples under ambient conditions using an ultra-high-resolution
implementation of scanning microwave impedance microscopy. We show that, quite
remarkably, although the scanning probe tip has a gross radius of ~100 nm, an
ultra-high spatial resolution in local conductivity profiles better than 5 nm
can be achieved. This resolution enhancement not only enables to directly
visualize the moire lattices in magic-angle twisted double bilayer graphene and
composite super-moire lattices, but also allows design path toward artificial
synthesis of novel moire superstructures such as the Kagome moire from the
interplay and the supermodulation between twisted graphene and hexagonal boron
nitride layers.
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