Nanoscale optics of twisted 2D materials
Moiré patterns are well-known phenomena in art, textiles and mathematics, which originate
from the overlay of two periodic patterns. Intriguingly, atomically thin materials can be stacked
on top of each other such that a new periodic pattern can emerge: the moiré superlattice. This
can result in a dramatic modification of the electronic and optical properties of twisted 2D
materials, compared to those of a single layer. The moiré superlattice can give rise to a plethora
of interesting phenomena such as topological bands  and many-body phases like
superconductivity and magnetism.
A tantalizing example is twisted bilayer graphene near the magic angle (MABG), which exhibits
flat superlattice minibands, effectively localizing electrons in a periodic lattice with a period of
about 15 nm. Several strongly correlated phases have been observed, including
superconductivity and the Mott-like insulating state .
In this talk, we give an overview of the nano-optical properties of stacked and twisted 2D
materials. Nanoscale optical techniques such as near-field optical microscopy reveal unique
observations of strongly confined propagating optical fields, topological domain wall
boundaries, and a different type of collective modes in charge neutral TBG near the magic angle
The freedom to engineer these so-called optical and electronic quantum metamaterials  is
expected to expose a myriad of unexpected phenomena.
 Ju et al., Nature (2015)
 Y. Cao et al. Nature 556, 80 (2018), Cao et al. Nature 556, 43 (2018)
 Hesp et al., in preparation
 Song, Gabor et. al., Nature Nanotechnology (2019)