A Single-Site Picture of Valence Fluctuation in Periodic Anderson Hamiltonian with Large Coulomb Correlation

Abstract

It is discussed that a competition between a formation of the singlet bound state at each site and an exchange interaction plays an important role in a periodic Anderson Hamiltonian with large Coulomb correlation. As the depth of f levels measured from the chemical potential is shallower, each f level site is more likely to behave independently; the depth is related with the number of f electrons per site (n_f). Therefore the system can be classified into three regimes: i) The first one is the independent f level regime where n_f is significantly less than one. ii) In the crossover regime where n_f is nearly one, each f level site behaves independently at high temperatures. However a band-like coherent behavior, or magnetic orderings are expected at low temperatures. iii) In the RKKY regime where n_f is very nearly one, magnetic orderings are expected at low temperatures.