[Show abstract][Hide abstract] ABSTRACT: Relative to single-band models, multiband models of strongly interacting electron systems are of growing interest because of their wider range of novel phenomena and their closer match to the electronic structure of real materials. In this brief review we discuss the physics of three multiband models (the three-band Hubbard, the periodic Anderson, and the Falicov-Kimball models) that was obtained by numerical simulations at zero temperature. We first give heuristic descriptions of the three principal numerical methods (the Lanczos, the density matrix renormalization group, and the constrained-path Monte Carlo methods). We then present generalized versions of the models and discuss the measurables most often associated with them. Finally, we summarize the results of their ground state numerical studies. While each model was developed to study specific phenomena, unexpected phenomena, usually of a subtle quantum mechanical nature, are often exhibited. Just as often, the predictions of the numerical simulations differ from those of mean-field theories.
Preview · Article · Aug 2006 · Communications in Computational Physics
[Show abstract][Hide abstract] ABSTRACT: To investigate possible pairing symmetries of Na0.3CoO2.1.3H2O, we study the single band extended Hubbard model on triangular lattice with variational Monte Carlo method. For the on site s-wave, the extended s-wave, the d-wave, the f-wave and the extended-f wave parings, we use the corresponding BCS type mean field wave functions with Jastrow factors as our trial wave functions. We found that in a suitable parameters region, the extended f-wave pairing is stabilized by the nearest-neighbor Coulomb interaction V. In order to further investigate the true ground state of this system we use the constrained path Monte Carlo (CPMC) method to calculate different correlation function in the ground state.
[Show abstract][Hide abstract] ABSTRACT: The periodic Anderson model is believed as a candidate of the minimal lattice models for itinerant ferromagnetism. Several numerical methods, including exactly diagonalization, constrained-path Monte Carlo method and mean field method, are employed to investigate the magnetic properties of the model in one dimension and two dimensions. By changing the band-filling, chemical potential of the impurity band and the hybridyzation between conduction band and impurity band, we found that in some parameter regions, different magnetic ordering exist. Some of results confirm the previous works and some are new.