When a collection of electronic excitations are strongly coupled to a single mode cavity, mixed light-matter excitations called polaritons are created. The situation is especiallyinteresting when the strength of the light-matter coupling Ωr is such that the coupling energy becomes close to the one of the bare matter resonance ω0. For this value of parameters, the system enters the so-called ultra-strong coupling regime, in which a number of very interesting physical effects were predicted. Using metamaterial coupled to two-dimensional electron gases, we have demonstrated that a ratio Ωr/ω0 close to or above unity can be reached.
We also demonstrated that such ultra-strong light-matter
coupling can be achieved using special geometries where the only less
than 100 electrons are effectively coupled to the resonator. One very
intriguing feature of the ultra-strong light-matter coupled system is the
prediction that photon pairs will be emitted through
non-adiabatic modulation of the coupling. To this end, we have realized
metamaterials based on highTc superconductors that retain a high quality
factor resonance for magnetic field up to 9T and coupled them to
two-dimensional electron gases.
We have also used transport to probe
the ultra-strong light-matter coupling. In these experiments, we have
used transport samples engineered with cavities and studied them under
very weak THz irradiation and now irradiation at all, showing an
influence of the cavity in both cases.
We have constructed a electro-optic
based setup that, we demonstrated recently, enables the probing of
the vacuum field in free space and retrieve its first order correlation
function in both space and time. Such experiment can be used also to
probe the unconventional ground state of the ultra-strongly coupled
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