Ferromagnetism in the two-dimensional periodic Anderson model - art. no. 184428

Using the constrained-path Monte Carlo method, we studied the magnetic prop erties of the two-dimensional periodic Anderson model for electron fillings between 1/4 and 1/2. We also derived two effective low-energy theories to assist in interpreting the numerical results. For 1/4 filling, we found tha t the system can be a Mott or a charge-transfer insulator, depending on the relative values of the Coulomb interaction and the charge-transfer gap bet ween the two noninteracting bands. The insulator may be a paramagnet or ant iferromagnet. We concentrated on the effect of electron doping on these ins ulating phases. Upon doping we obtained a partially saturated ferromagnetic phase for low concentrations of conduction electrons, if the system were a charge-transfer insulator, we would find that the ferromagnetism is induce d by the well-known Ruderman-Kittel-Kasuya-Yosida interaction. However, we found a novel correlated hopping mechanism inducing the ferromagnetism in t he region where the nondoped system is a Mott insulator. Our regions of fer romagnetism spanned a much smaller doping range than suggested by recent sl ave boson and dynamical mean-field theory calculations, but they were consi stent with that obtained by density-matrix renormalization group calculatio ns of the one-dimensional periodic Anderson model.