Abstract
The observation of giant Rydberg excitons in cuprous oxide up to a principal quantum number of by T. Kazimierczuk et al. [Nature (London) 514, 343 (2014)] inevitably raises the question whether these quasiparticles must be described within a multipolariton framework since excitons and photons are always coupled in the solid. In this paper we present the theory of exciton-polaritons in . To this end we extend the Hamiltonian which includes the complete valence-band structure, the exchange interaction, and the central-cell corrections effects, and which has been recently deduced by F. Schweiner et al. [Phys. Rev. B 95, 195201 (2017)], for finite values of the exciton momentum . We derive formulas to calculate not only dipole but also quadrupole oscillator strengths when using the complete basis of F. Schweiner et al., which has recently been proven as a powerful tool to calculate exciton spectra. Very complex polariton spectra for the three orientations of along the axes , , and of high symmetry are obtained and a strong mixing of exciton states is reported. The main focus is on the ortho-exciton-polariton, for which pronounced polariton effects have been measured in experiments. We set up a matrix model, which accounts for both the polariton effect and the -dependent splitting, and which allows treating the anisotropic polariton dispersion for any direction of . We especially discuss the dispersions for being oriented in the planes perpendicular to and , for which experimental transmission spectra have been measured. Furthermore, we compare our results with experimental values of the -dependent splitting, the group velocity, and the oscillator strengths of this exciton-polariton. The results are in good agreement. This proves the validity of the matrix model as a useful theoretical model for further investigations on the ortho-exciton-polariton.
- Received 15 August 2017
- Revised 17 October 2017
DOI:https://doi.org/10.1103/PhysRevB.96.245202
©2017 American Physical Society