Accurate modeling of electron-hole binding in CuCl. I. Exciton states

We present an accurate variational approach for calculating the ground and excited exciton states in CuCl, and provide detailed comparison with measured polariton energies of excited exciton states. Computed exciton energies and oscillator strengths allow us to reproduce the polariton dispersion of up to four exciton states with unprecedented accuracy. A reinterpretation of the observed 1s-exciton binding energy shows that the actual Coulomb energy in the exciton ground state is more than 50% larger than the observed binding energy, with important consequences for calculation of exciton complexes such as the biexciton.