Dynamic Jahn-Teller interaction withΓ5phonons in the ground state ofCu2+

Abstract

Optical absorption and emission measurements of Cu 2ϩ as a substitutional impurity in cubic ZnS and ZnTe are analyzed by means of an electron-phonon coupling model. The 2 D term of Cu 2ϩ is split by a crystal field of tetrahedral symmetry into a 2 ⌫ 5 orbital triplet and a 2 ⌫ 3 orbital doublet. Optical transitions have been observed between these two multiplets in ZnS:Cu 2ϩ and within the 2 ⌫ 5 ground state in ZnTe:Cu 2ϩ . The theoretical model is based on crystal-field theory and includes the spin-orbit interaction and a dynamic Jahn-Teller interaction between the electronic 2 ⌫ 5 states and a transverse acoustic phonon of ⌫ 5 symmetry. Starting from the ten spin-orbit wave functions appropriate to the orbital triplet and doublet manifolds, the symmetryadapted vibronic basis is constructed and used to diagonalize the Hamiltonian matrix. Phonon overtones up to nϭ14 are included to ensure convergence of the energy eigenvalues. The measured positions and relative intensities of the spectral lines are described with good accuracy by the theoretical model, including covalency effects. In ZnS, comparison between theory and experiment yields the following values of the physical parameters: the crystal-field splitting ⌬ϭ5990.6 cm Ϫ1 , the spin-orbit coupling constants 1 ϭϪ667 cm Ϫ1 and 2 ϭϪ830 cm Ϫ1 , the phonon energy បϭ73.5 cm Ϫ1 , and the Jahn-Teller stabilization energy E JT ϭ474.5 cm Ϫ1 . The corresponding parameters in ZnTe are ⌬ϭ6000 cm Ϫ1 , 1 ϭϪ888 cm Ϫ1 , 2 ϭϪ830 cm Ϫ1 , បϭ38.8 cm Ϫ1 , and E JT ϭ468.5 cm Ϫ1 .

The effect of electron-phonon interaction in iron-doped III-V cubic semiconductors

“…We proposed a new interpretation of both the emission and absorption spectra of Fe 2+ in InP and GaP, which also accounts for the isotopic shifts of the zero-phonon line observed in this compound. Finally, the spin-orbit coupling constants deduced from our calculations show that the covalent character of the bonds is much more important in III-V compounds than in II-VI compounds such as ZnS [24].…”