Dresden 2003 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 11: Postersitzung II (Metall-Isolator-Überg
änge, Phasenüberg
änge in Quantensystemen, Theorie: Systeme korrelierter Elektronen)

TT 11.42: Poster

Dienstag, 25. März 2003, 14:30–19:00, P2c, P2d

Lattice-dynamics in quasi-1D-models with orbital ordering — •Andreas Friedrich and Wolfram Brenig — Institut für Theoretische Physik, Technische Universität Braunschweig, Germany

We study the interplay of spin, orbital and lattice degrees of freedom in quasi-one dimensional systems by considering the Kugel-Khomskii model on a chain coupled to phonons. In the vicinity of the dimer point of the latter model we analyze the excitation spectrum by mapping of the spin and orbital degrees of freedom to a gas of interacting bond-bosons which can be treated by conventional diagrammatic techniques. Particular emphasis will be put on the renormalization of the phonon propagator due to coupling to the orbital and magnetic excitations. Considering both, ferro- and antiferro-orbital ordering we will show that the appearance of orbiton shake-up processes in the phonon spectrum is sensitive to the type of Jahn-Teller distortion. The relevance of our results to optical experiments on low dimensional transition metal compounds will be discussed.