Two-dimensional (2D) materials offer extraordinary potential for control of light and light-matter interactions at the atomic scale. In this talk, we will show a new toolbox to exploit the collective motion of light and charges as a probe for topological, hyperbolic and quantum phenomena.We twist or nanostructure heterostructures of 2D materials that carry optical excitations such as excitons, plasmons or hyperbolic phonon polaritons. Nanoscale optical techniques such as near-field optical microscopy reveal with nanometer spatial resolution unique observations of topological domain wall boundaries, hyperbolic phononic cavities [1], and interband collective modes in charge-neutral twisted-bilayer graphene near the magic angle [2]. The freedom to engineer these so-called optical and electronic quantum metamaterials [3] is expected to expose a myriad of unexpected phenomena.
Intriguingly, we define nanoscale phonon polaritonic cavities, where the resonances are not associated with the eigenmodes of the cavity. Rather, they are multi-modal excitations whose reflection is greatly enhanced due to the interference of constituent modes. We will also show a new type of graphene-based magnetic-resonance that we use to realize single, nanometric-scale cavities of ultra-confined acoustic graphene plasmons [4]. We reach record-breaking mode volume confinement factors of ∼ 5 · 10−10. This AGP cavity acts as a Mid-infrared nanoantenna, which is efficiently excited from the far-field, and electrically tunable over an ultra-broadband spectrum. Finally, we present near-unity light absorption in a monolayer WS2 van der Waals heterostructure cavity [5].
[1] Herzig Sheinfux et al., in preparation
[2] Hesp et al., Arxiv 1910.07893
[3] Song, Gabor et. al., Nature Nanotechnology (2019)
[4] Epstein et al., Arxiv 2002.00366
[5] Epstein et al., Arxiv 1908.07598
Prof. Frank Koppens obtained his Ph.D. in experimental physics at Delft University, at the Kavli Institute of Nanoscience, The Netherlands. After a postdoctoral fellowship at Harvard University, Since August 2010, Koppens is a group leader at the Institute of Photonic Sciences (ICFO). The quantum nano-optoelectronics group of Prof. Koppens focuses on both science and technology of novel two-dimensional materials and quantum materials. Prof. Koppens is vice-chairman of the executive board of the graphene flagship program, a 1000 Million Euro project for 10 years. He is also the leader of the optoelectronics work package within the flagship. Prof. Koppens holds a GSMA Chair with activities related to the Mobile World Congress. 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 2012, the national award for research in Spain, and the IUPAP young scientist prize in optics. In total, Koppens has published more than 70 refereed papers (H-index above 47), with more than 35 in Science and Nature family journals. Total citations >17.500 (google scholar).
