Energy of strongly correlated electron systems

K. W. Becker, Peter Fulde

Taeho Jo, Arata Tanaka, 城 健男 +1 more

Dmitry V. Berkov, S. V. Meshkov

Sadamichi Maekawa, Takami Tohyama, Seiji Yunoki

Peter Fulde, Hermann Stoll, K. Kladko

We formulate the calculation of the ground-state wavefunction and energy of a system of strongly correlated electrons in terms of scattering matrices. A hierarchy of approximations is introduced which results in an incremental expansion of the energy. The present approach generalizes previous work designed for weakly correlated electronic systems. 1 I.

Dimitrios Galanakis

In this thesis we are going to study the properties of strongly correlated electron systems (SCES) using analytical, phenomenological and computational methods. In the introductory chapter we will discuss generally the problem of strongly correlated electron systems and the methods that are used to analyse their behavior. In chapter 2, we discuss the derivation of low energy effective theories by using perturbation theory. In chapter 3, we point out potential problems with perturbative techniques used to construct low energy theories for SCES. In chapter 4, we introduce an important class of materials, namely the cobaltates NaxCoO2 and we discuss the experiments that establish their strongly correlated electron nature. The cobaltates exhibit a novel insulating state at x = 0.5 which corresponds to a 3/4 filled band. This state is analyzed phenomenologically in chapter 5. In chapter 6, we introduce a non perturbative technique appropriate for strongly correlated electron systems, the Dynamical Mean Field Theory (DMFT) and its cluster extension. The results of the application of cluster DMFT on the cobaltates are presented in chapter 7.