Groundstate-calculation for the T-t Jahn-Teller system by an exponential transformation approach

The dynamical T-t Jahn-Teller problem is handled by a canonical exponential transformation exp (- S) H exp (S). The groundstate wavefunction of the diagonal part of H is given in the transformed and original space. Its expectation value for the total Hamiltonian is shown to agree with the exact numerical groundstate results up to intermediate coupling strengths. For strong coupling values the dominant k power still seems to be given correctly. However, in this limiting case exact results can be derived by a second transformation. Both types of transformations lead in a combined form to very accurate groundstate energies, which can be fitted with respect to the given numerical values.