Effects of uniaxial strain on the exciton spectra of CuCl, CuBr, and CuI

We have investigated the effects of large static uniaxial strain, up to ∼3 GPa, on the excitons $Z_{1,2}$ and $Z_3$ of the cuprous halides using a gasketed diamond anvil cell. From the shifts and the stress-induced splittings of these excitons, we have obtained orbital and spin-orbit hydrostatic and shear deformation potentials. We have found that the shear deformation potential $d=d_1+2\mathrm{}{d}_2$ is positive for CuCl and negative for CuBr and CuI. Our measurements also show that the deformation potential of the spin-orbit splitting, $\frac{d{\Delta }_0}{d\ln V}$, is negative for all three copper halides. From the pressure dependence of the intensity ratio $\frac{I_{Z_{1,2}}}{I_{Z_3}}$ we have been able to obtain reliable values for the electron-hole exchange energy of the edge excitons in CuCl and CuBr.