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TT: Tiefe Temperaturen

TT 31: Correlated Electrons: Metal Insulator Transition - Part 2

TT 31.16: Talk

Thursday, March 30, 2006, 18:00–18:15, HSZ 301

Effective model for E⊗β-coupling and electron-electron interaction — •Daniela Schneider, Klaus Ziegler, and Karl-Heinz Höck — Institut für Physik, Universität Augsburg, 86135 Augsburg

We investigate the effect and interplay of orbital and spin degrees of freedom. The model takes electron-electron interaction and electron-phonon coupling of the E⊗β-type into account. The hopping is considered as orbital conserving. We derive an effective spin-orbital Hamiltonian at quarter filling through projection on singly occupied sites, treating the phonons quantummechanically, and discuss the symmetry of the initial and the effective model. Furthermore we identify the similarities and differences to the purely electronic and the adiabatic effective Hamiltonian. The anisotropy in the orbital part reflects the difference of spin and orbital exchange. The groundstate properties are studied for small clusters and the influence of the electron-phonon interaction and the spin and orbital occupancy are investigated. For dimers we compare the results obtained by exact diagonalisation with those achieved with the effective Hamiltonian.

This work is supported by DFG (SFB 484).