Nanoscale optics of 2D material superlattices

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 [1] and many-body phases like superconductivity and magnetism [2].
In this talk, we give an overview of the nano-optical properties of 2D material superlattices, obtained by twisting or nanostructuring. Nanoscale optical techniques such as near-field optical microscopy reveal unique observations of topological domain wall boundaries, hyperbolic phononic lattices, and interband collective modes in charge neutral TBG near the magic angle [3]. The freedom to engineer these so-called optical and electronic quantum metamaterials [4] is expected to expose a myriad of unexpected phenomena.
References
[1] Ju et al., Nature (2015)
[2] Y. Cao et al. Nature 556, 80 (2018), Cao et al. Nature 556, 43 (2018)
[3] Hesp et al., Arxiv 1910.07893
[4] Song, Gabor et. al., Nature Nanotechnology (2019)