Free Excitons and Polaritons

Group theory arguments and the direct product of the group representations of the band symmetries (F7 for the conduction band, F9 for the A valence band, upper F7 for 

B valence band, and lower F7 for C valence band) will result in the following intrinsic exciton ground-state symmetries  

Using (1, one can also estimate the effective exciton Bohr radius from 

Among these reports, there exists a discrepancy in the quoted values for the spin-orbit interaction energy and the exciton binding energies, which most likely may have its genesis in the difficulty of interpreting the complex spectra near the band edge. 

T ark et al. [5] (platelets and hulk crystals grown from the vapor phase). 

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