Radiative Renormalizations for Excitonic Molecules

The influence of the polariton effects on the internal structure of an excitonic molecule ($\mathrm{xx}$) is examined by the solution of the new $\mathrm{xx}$ Schrödinger equation which includes the polariton effects self-consistently. In 3D (CuCl) the radiative renormalizations yield a nonparabolic $\mathrm{xx}$ dispersion with infinite effective $\mathrm{xx}$ mass at zero momentum; in quasi-2D (GaAs) they give rise to a "Mexican hat" structure in the $\mathrm{xx}$ dispersion at small momenta together with a considerable increase of both the $\mathrm{xx}$ binding energy ${\epsilon }^{\mathrm{xx}}$ and the inverse $\mathrm{xx}$ radiative lifetime ${\Gamma }^{\mathrm{xx}}$. In quasi-1D the influence of the polariton effects is so strong that the $\mathrm{xx}$ exists only as a broad resonance (${\epsilon }^{\mathrm{xx}}\sim {\Gamma }^{\mathrm{xx}}$).