A new application of the diamond anvil cell: Measurements under uniaxial stress

We present optical absorption measurements on thin films of CuCl and CuBr at 100K under uniaxial stress up to ～3.0 GPa. The thin films were prepared by evaporating onto the inner face of one diamond of a diamond anvil cell. From the splitting of the excitons we were able to determine the shear deformation potential d = -0.69 ± 0.03 eV for CuBr and d = +0.45 ± 0.08 eV for CuCl. Our measurements indicate also that the spin-orbit splitting increases in both materials with increasing pressure. A new shear-induced phase is found for CuCl above 4.8 GPa.