Berlin 2005 – wissenschaftliches Programm
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TT: Tiefe Temperaturen
TT 16: Posters Correlated Electrons, Measuring Devices, Cryotechnique
TT 16.73: Poster
Samstag, 5. März 2005, 11:00–16:30, Poster TU C
Orbital excitations in transition-metal compounds — •R. Rückamp1, A. Gössling1, M. Grüninger1, H. Roth1, A. Freimuth1, L. Jongen2, A. Möller2, G. Meyer2, T.T.M. Palstra3, A. Nugroho3, and S.-W. Cheong4 — 1II. Physikalisches Institut, Universität zu Köln — 2Institut für Anorganische Chemie, Universität zu Köln — 3Materials Science Centre, University of Groningen — 4Department of Physics & Astronomy, Rutgers University, New Jersey
In recent years orbital physics has attracted much interest since novel phenomena - such as an orbital liquid state or new elementary excitations in an orbitally ordered state - have been predicted. In order to observe these phenomena, one has to look for a system in which the orbital (electron-electron) coupling dominates over the coupling to the lattice (Jahn-Teller effect). We have studied orbital excitations in the optical conductivity spectra of several transition-metal compounds such as RTiO3, RVO3, TiOX or Y2BaNiO5 by measuring both transmittance and reflectance of single crystals. The energies of the orbital (d-d) transitions are compared with the results of a point-charge model including the hybridisation with the ligand ions. We find good agreement between experiment and theory, which suggests that the coupling to the lattice is dominant in the studied compounds.