Trion-polaritons : How strong coupling to a cavity changes the orbital and spin properties of trions

The elementary optical excitations of a two-dimensional electron system strongly coupled to a microcavity are trion-polaritons. Using a variational approach, we demonstrate that the competition between Coulomb interaction and light-matter coupling plays a crucial role in determining the lowest-energy orbital and spin properties of trion-polaritons. When the light-matter interaction exceeds the bare trion binding, singlet and triplet trion states are mixed due to a cavity-mediated spin-orbit effect, which in turn results in a strong increase of the outer electron Bohr radius. In this strong cavity coupling regime, the trion-polariton consists of an exciton-polariton surrounded by a weakly bound electron and is reminiscent of a coherent Rydberg excitation.