Spin-selective strong light–matter coupling in a 2D hole gas-microcavity system

The interplay between time-reversal symmetry breaking and strong light–matter coupling in two-dimensional (2D) gases brings intriguing aspects to polariton physics. This combination can lead to a polarization/spin-selective light–matter interaction in the strong coupling regime. Here we report such a selective strong light–matter interaction by harnessing a 2D gas in the quantum Hall regime coupled to a microcavity. Specifically, we demonstrate circular-polarization dependence of the vacuum Rabi splitting, as a function of magnetic field and hole density. We provide a quantitative understanding of the phenomenon by modelling the coupling of optical transitions between Landau levels to the microcavity. This method introduces a control tool over the spin degree of freedom in polaritonic semiconductor systems, paving the way for new experimental possibilities in light–matter hybrids. Strong coupling of a 2D hole gas in the quantum Hall state dressed with a microcavity mode is studied, showing that tuning the strength of the magnetic field, and therefore the density of states in the system, can select specific spin-dependent light–matter coupling.