Combining a fully switchable THz superconducting metamaterial with a 2DEG for ultra-strong coupling

We study terahertz (THz) superconducting split-ring resonators showing that the resonance of the metasurface is fully switchable via the superconducting transition, exhibiting a resonance only below the critical temperature and a critical magnetic field. Combining this metamaterial with a two-dimensional electron gas (2DEG), which is forming Landau levels in magnetic field, we aim for an ultra-strongly coupled system. We report on experiments showing strong coupling between the excited cavity mode and the 2DEG and we discuss possible scenarios for observing ultra-strong coupling with the fundamental LC mode.