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TT: Fachverband Tiefe Temperaturen
TT 27: CE: Poster Session
TT 27.51: Poster
Mittwoch, 24. März 2010, 14:00–18:00, Poster D1
High-frequency tails and the decay rate of high-energy excitations in correlated systems — •Matthias Sitte1 and Lev Ioffe2 — 1Institut für Theoretische Physik, Universität zu Köln, 50937 Köln — 2Center for Materials Theory, Department of Physics and Astronomy, Rutgers University, Piscataway NJ 08854 USA
For energies much larger than the bandwidth, the lifetime of a highly excited state becomes exponentially large. Similarly, the high-frequency tails of correlation functions decay exponentially. This response is due to a collective excitation of many discrete degrees of freedom. Such a many-particle scattering process describes, e.g., the decay of doublons (doubly occupied sites) in ultra-cold atom gases in optical lattices, or the NMR relaxation mechanism in large magnetic fields. Here, we investigate the shape of correlation functions at high frequencies. In particular, we consider the spin 1/2 Heisenberg XXZ chain, a paradigm model for strongly correlated systems, which can be realized, e.g., in spin chain systems and in ultra-cold atom gases using two-level systems. Using exact diagonalization methods we calculate the correlation function of the staggered magnetization in frequency space and compare to analytical approaches.