Dresden 2011 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 52: CE: Low-dimensional Systems - Models 1
TT 52.5: Talk
Thursday, March 17, 2011, 15:15–15:30, HSZ 105
A study of coupled spin-orbital physics in a one-dimensional model — •Alexander Herzog1,2, Andrzej Michal Oles1,3, Peter Horsch1, and Jesko Sirker2 — 1Max Planck Institut für Festkörperforschung, Stuttgart, Germany — 2Department of Physics and Research Center Optimas, University of Kaiserslautern, Kaiserslautern, Germany — 3Marian Smoluchowski Institute of Physics, Krakow, Poland
We study the dynamics and thermodynamics of a one-dimensional spin-orbital model relevant for transition metal oxides. For antiferromagnetic superexchange we investigate how spin-wave excitations are affected by coupled spin-orbital excitations using a boson-fermion representation. We contrast a mean-field decoupling approach with results obtained by treating the spin-orbital coupling perturbatively. Within the latter approach we find a significant broadening and additional structures in the dynamical spin structure factor caused by the coupling of spin excitations to orbital fluctuations leading to a Kohn anomaly in the spin-wave dispersion. Moreover the spin-orbital coupling induces a redistribution of entropy from low to intermediate temperatures as is confirmed by comparing our perturbative results for the specific heat with a numerical solution of the model obtained by the density-matrix renormalization group.