A ONE-MODE INTERMEDIATE-COUPLING JAHN-TELLER CALCULATION FOR AN ORBITAL DOUBLET IN CUBIC SYMMETRY
HOFFMAN, JOHN RUSSELL
Doctor of Philosophy
A two-step matrix formulation is used to analyze the intermediate-coupling problem for an orbital doublet coupled to one doubly-degenerate vibrational mode (a Jahn-Teller doublet). First the linear-coupling problem is formulated in terms of a basis that reduces the effective Hamiltonian to blocks of tridiagonal matrices. The eigenfunctions for the lower states from this first step are then used as a new basis when including nonlinear-coupling and anharmonic terms. The energies are computed and the final eigenfunctions are used to compute reduction factors and polarizability matrix elements among many of the lower-energy states. Linear coupling, nonlinear coupling and anharmonicity are varied independently over a wide range. Even though these calculations are accurate (being equivalent to diagonalizing a matrix of order up to 16,000) and cover the intermediate-coupling region, there are no important deviations from theories using strong-coupling approximations for the lowest energy states which are important in experiment.
Condensed matter physics