Münster 1997 – scientific programme

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TT: Tiefe Temperaturen

TT 14: Postersitzung II: Korrelierte Systeme(1-40), Theorie der Supraleitung(41-50), Metall-Isolator-Übergang, Lokalisierung(51-66), Niederdimensionale Systeme, Quantenhalleffekt(67-80), Pinning, kritische Ströme und Vortexdynamik(81-93), HTSL-Drähte und -Bänder(94-98), Massive HTSL(99-104), supraleitende Borkarbide(105-109)

TT 14.25: Poster

Wednesday, March 19, 1997, 15:00–18:30, Z1

Holstein Model in Infinit Dimensions — •P. Benedetti and R. Zeyher — Max Planck Institut f"ur Festk"orperforschung, Heisenbergstr. 1, D-70569 Stuttgart

We present the result of a study of polaron formation and the associated effects in the phonon spectrum, in many-electrons systems. Considering the Holstein model (electrons interacting locally with dispersionless, quantized phonons, with a coupling λ) we make use of the dynamical mean field-theory, that becomes exact in the limit of infinite dimension. We choose a Lorentzian density of states, corresponding to long-range hopping on a hypercubic lattice. After integrating out the electronic degrees of freedom, an effective action for the phonons is obtained and a gradient expansion performed. The gradients in time are controlled by Migdal’s parameter m, those in space by the assumption of infinite dimensions. Using eigenfunctions of the local part, we map the problem in a generalized spin model. Detailed numerical results for the isotope effect, phonons softening and its spectral function are given and the phase boundary for density wave formation discussed.