Experimental study of plasmon polaritons in topological insulators and Weyl Semi-Metals.

ended

Polaritons are joint excitations of light and matter and constitute an important field of study in optics. Historically, many new types of polaritons have been discovered by inspecting novel and interesting material systems, with graphene plasmons being a prominent example. Project TOPLASMON aims to study and harness the polaritons in an even newer material category - topological materials - which have recently been discovered and are intensively studied in condensed matter physics. These materials include topological insulators, which have conducting edges but insulating bulks, and Weyl Semimetals, which support unique Fermi-arc states. At the heart of project TOPLASMON is a novel measurement system, which combines a recently invented cryogenic scanning near field microscope with a THz laser and detector. This setup will allow, for the first time, the observation of topological polaritons of several varieties: (1) Chiral polaritons in topological insulators which exhibit reduced backscattering from defects. Specifically, I will working with the recently realized 2D topological insulators. (2) Fermi-arc Polaritons in Weyl Semimetals, whose dispersion is tied in with the properties of the underyling crystal, thereby probing the properties of these new materials. These polaritons are expected to have an in-plane hyperbolic dispersion and may even lead to realization of miniaturized optical isolators, leading to an important technological breakthrough. (3) Strong plasmonic resonances. I will study plasmon-polariton excitations in topological material, at frequencies near the plasmonic resonance. Empowered by the exceedingly long electron scattering times measured in several recent experiments, highly confined plasmons with unprecedentedly long propagation distances are exoected, a dramatic result for both science and technology. This proposal is therefore set to open a new study area at the forefront of research both in condensed matter and nanophotonics.