Non-locality and single meta-atom spectroscopy in THz Landau polaritons

We will discuss, theoretically and experimentally, the existence of a limit to possibility arbitrarily increasing electromagnetic confinement in polaritonic systems, where strongly sub-wavelength fields can excite continuum high-momenta propagative magnetoplasmons. This leads peculiar nonlocal effects, as certain features disappear system enters regime discrete-to-continuum strong coupling. well present experiments reporting spectroscopy single, ultrastrongly coupled, highly subwavelength resonator operating at 300 GHz.