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TT: Fachverband Tiefe Temperaturen

TT 6: Postersession Correlated Electrons: (General) Theory, Low-Dimensional Systems, Kondo Physics, Heavy Fermions, Quantum-Critical Phenomena

TT 6.13: Poster

Montag, 23. März 2009, 13:00–16:45, P1A

Phonon renormalization from local and transitive electron-lattice couplings in strongly correlated systems — •Ernst von Oelsen¹, Andrea Di Ciolo^2,3, Jose Lorenzana^2,3,4, Marco Grilli^2,3, and Götz Seibold¹ — ¹Institut für Physik, BTU Cottbus, PBox 101344, 03013 Cottbus, Germany — ²Dipartimento di Fisica, Università di Roma “La Sapienza”, P. Aldo Moro 2, 00185 Roma, Italy — ³SMC-Istituto Nazionale di Fisica della Materia — ⁴ISC-Consiglio Nazionale delle Ricerche

Within the time-dependent Gutzwiller approximation (TDGA) applied to Holstein- and SSH-Hubbard models we study the influence of electron correlations on the phonon self-energy. For the local Holstein coupling we find that the phonon frequency renormalization gets weakened upon increasing the onsite interaction U for all momenta. In contrast, correlations can enhance the phonon frequency shift for small wave-vectors in the SSH-Hubbard model. Moreover the TDGA applied to the latter model provides a mechanism which leads to phonon frequency corrections at intermediate momenta due to the coupling with double occupancy fluctuations. Both models display a shift of the nesting-induced to a q=0 instability when the onsite interaction becomes sufficiently strong and thus establishing phase separation as a generic phenomenon of strongly correlated electron-phonon coupled systems.