Strong coupling expansion approach to the Hubbard and periodic Anderson Models

Marcel Franz, M. Noga

Jürgen Stein

S. Pairault, David Sénéchal, A.–M. S. Tremblay

Mario E. Foglio, Marcos Sergio Figueira

The diagrammatic cumulant expansion for the periodic Anderson model with infinite Coulomb repulsion is considered here for an hypercubic lattice of infinite dimension . The nearest neighbour hopping of the uncorrelated electrons is described exactly by a conduction band, while two different models of hybridization are treated as a perturbation. The same type of simplifications obtained by Metzner for the cumulant expansion of the Hubbard model in the limit of , are also shown to be valid for the periodic Anderson model. The derivation of these properties had to be modified because of the exact treatment of the conduction band.

N. A. Kuleeva, É. Z. Kuchinskiǐ, Michael V. Sadovskii

We present a brief review of our studies of disorder influence upon Ginzburg-Landau expansion coefficients in Anderson-Hubbard model with attraction in the framework of the generalized DMFT + Σ approximation. A wide range of attractive potentials U is considered from weak coupling limit, where superconductivity is described by BCS model, to the limit of very strong coupling, where superconducting transition is related to the Bose-Einstein condensation of compact Cooper pairs, which are formed at temperatures significantly higher than the superconducting transition temperature, as well as the wide range of disorders from weak to strong, when the system is in the vicinity of Anderson transition. For the same range of parameters we study in detail the temperature behavior of orbital and paramagnetic upper critical field H c2 ( T ), which demonstrates the anomalies due both to the growth of attractive potential and to the effects of strong disordering.

V. A. Moskalenko