Résumé
We report the observation of Dirac-Landau polaritons via THz
magnetoreflectivity spectroscopy, demonstrating strong coupling between
cyclotron transitions of two-dimensional Dirac fermions in HgTe quantum wells
and optical cavity modes. We demonstrate efficient nonlinear
electroluminescence, characterized by a strongly out-of-equilibrium polariton
distribution dominated by emission from the upper polariton branches. Model
calculations, based on the nonlinear dependence of the emission intensity and
spectral narrowing with bias voltage, indicate a polariton occupancy per mode
close to unity, with a significant contribution from stimulated polariton
emission. These findings open promising prospects for the development of
Dirac-Landau polariton condensates and low-threshold, tunable terahertz
polariton lasers based on cyclotron emission.