Polaritons and ultrasmall cavities in twisted 2D material heterostructures
Max Planck Lecture on Non-Equilibrium Quantum Phenomena
- Date: Nov 11, 2020
- Time: 15:00 - 16:00
- Speaker: Frank Koppens
- Location: online via Zoom
- Host: Andrea Cavalleri, Angel Rubio
Two-dimensional (2D) materials offer extraordinary potential for control of light and light-matter interactions at the atomic scale. Twisted 2D materials has recently attracted a lot of interest, due to the capability to induce moiré superlattices and discovery of electronic correlated phases [1,2]. In this talk, we present nanoscale optical techniques such as near-field optical microscopy, and reveal with nanometer spatial resolution unique observations of topological domain wall boundaries  and interband collective modes in charge neutral twisted-bilayer graphene 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.
We will also show record-small nanoscale polaritonic cavities [4,5], where the resonances are not associated to the eigenmodes of the cavity. Rather, they are multi-modal excitations whose reflection is greatly enhanced due to the interference of constituent modes. We demonstrate mid-IR cavities with volumes more than a billion below the free-space mode volume, while maintaining quality factors above 100.
 Song, Gabor et. al., Nature Nanotechnology (2019)
 Cao et al., Nature (2018)
 Hesp et al., Arxiv 1910.07893
 Hesp et al., in preparation
 Epstein et al., Science (2020)
 Herzig Sheinfux et al., in preparation
Prof. Frank Koppens obtained his PhD in physics at Delft University, The Netherlands. After a postdoctoral fellowship at Harvard University, since 2010, Koppens is group leader at the Institute of Photonic Sciences. Koppens has received five ERC awards: the ERC starting grant, the ERC consolidator grant, and three ERC proof-of-concept grants. Other awards include the Christiaan Hugyensprijs, the national award for research in Spain, the IUPAP young scientist prize in optics and the ACS young investigator award. In total, Koppens has published more than 80 refereed papers (H-index above 52), with more than 40 in Science and Nature family journals. Total citations >20.000 (google scholar). Koppens is workpackage leader and vice-chairman of the executive board of the graphene flagship program, a 1000 Million Euro project for 10 years. He is on the Clarivate list of highly cited researchers (ranked in top 1% by citations).