Live From New York: Polaritons in van der Waals Materials
In 1944 Hans Bethe reported on “the diffraction of electromagnetic radiation by a hole small compared with the wave-length.” 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 graphene and other atomically layered van der Waals materials. Central to the nano-optical exploration of quantum materials is the notion of polaritons: hybrid light-matter modes that are omnipresent in polarizable media. Infrared nano-optics allows one to directly image propagating polaritons yielding rich insights into the electronic phenomena of the host material supporting polaritons. We utilized this novel polaritonic approach to investigate the physics of ballistic electrons in graphene including the search for quasi-relativistic Doppler-Fizeau effect. If time permits, I will also discuss our recent advances with multi-messenger nano-imaging: a scanning probe approach for correlating in time and space images produced by diverse contrast mechanisms and carrying complementary massages about the studied phenomena.