In 1944 Hans Bethe reported on “the diffraction of electromagnetic radiation by a hole small compared with the wave-length” [Physical Review 66, 163 (1944)]. This seminal paper was among the early precursors to a new and vibrant area of research: near field nano-optics. I will discuss recent nano-optical experiments on quantum materials including graphene and other atomically layered crystals. Central to the nano-optical exploration of quantum materials is the notion of polaritons: hybrid light-matter modes that are omnipresent in polarizable media [Nature Materials 16, 1077 (2017)]. Infrared nano-optics allows one to directly image polaritonic standing waves yielding rich insights into the electronic phenomena of the host material supporting polaritons [Science 354, 195 (2016)]. We utilized this novel general approach to investigate the physics of ballistic electronic transport in graphene [Nature 557, 530 (2018)] and of topological conducting channels also in graphene [Science 362, 1153 (2018)].
Website: http://infrared.cni.columbia.edu
