ATTENTION : jour et salle inhabituels / unusual room and day

Séminaire commun au LPS (Orsay), CPhT (X), SPhT (CEA/Saclay)
Gabriel KOTLIAR. Strongly Correlated Electron Materials: A Dynamical Mean Field Perspective.
Strongly correlated electron materials display a remarkable set of properties, such as metal to insulator transitions in transition metal oxides and in organic materials as well as high temperature superconductivity in materials containing copper oxides layers to name a few. These interesting materials cannot be described within the standard model of solid state physics and require a new theoretical framework for describing its physical properties.
Over the last fifteen years, a new approach to the strong correlation problem, the Dynamical Mean Field Theory (DMFT) has emerged. Inspired by techniques in statistical mechanics it stresses the use of local impurity problems as reference system to describe extended strongly correlated systems.
In this talk, we will introduce the ideas of dynamical mean field theory and its cluster extensions and will illustrate them with an application to the Mott transition problem in the organics and in the copper oxides high temperature superconductors.
(Pause café de 30 minutes)
Fabien ALET. Interacting Bosons on a Lattice
In addition to the connection to the physics of Cooper pairs in high-T$_c$ superconductors, the interest in lattice models of interacting bosons has been rejuvenated due to several recent experimental achievements, e.g. in cold atomic gases trapped on optical lattices and in solid $^4$He. In this talk, I will make a review of the various phases and (quantum) phase transitions we can expect for models of interacting bosons on a lattice. I will present highly-accurate numerical results obtained on such systems, and when possible discuss the relevance to experimental findings. Recent developments in the field, including supersolids on the triangular lattice and the possible existence of exotic quantum phase transitions, will also be reviewed.

CPHT-X, SPHT/Saclay, Center for Materials Theory (Rutgers Univ.) / LPT Toulouse