Effects of Uniaxial Stress on Excitons in CuCl

The effects of uniaxial stress on the exciton reflection spectra of zinc-blende CuCl have been investigated experimentally and theoretically. From a comparison of the experimental results with a theory which takes account of the strain, spin-exchange, and stress-induced k-linear terms, it is established that the stress-induced k-linear term is playing an essential role in the anomalous transverse-longitudinal mode mixing of the Z₃ exciton observed in a configuration of →P∥[001] and →K∥[110]. The coefficient of the stress-induced k-linear term is estimated to be about 10^-7 eV cm, which seems to be reasonable in comparison with the previously known k-linear term in CdS. It is further proved that this effect is closely related to a stress-induced gyrotropy in deformed CuCl from macroscopic considerations on the dielectric tensor with a spatial dispersion linear in →K. Additional contribution of the effect of an off-axis incidence in case of lower symmetry is also discussed.