Exciton-light coupling and redisribution of the light-hole exciton states in crystals with a degenerate valence band

In crystals with a degenerate valence band, intrinsic wave vector-dependent coupling occurs between the ground states of heavy-hole and light-hole excitons and their excited states. For a heavy-hole exciton, this mixing leads to a slight enhancement of its exciton-light coupling as the wave vector increases. The exciton-light coupling of the light-hole exciton decreases rapidly with increasing wave vector owing to the intrinsic coupling with the excited states of the heavy-hole exciton.