Occupancy Fluctuation Effects on 3D Hubbard Model at Quarter Filling within Dynamical Mean-Field Theory

Research on materials classified into strongly-correlated systems has become a crucial subject due to the strong interactions among the material constituents yielding various exotic physical properties and phenomena. There have been many computational methods developed to address the properties of such systems accurately within the Hubbard model, but most of them require a lot of computational costs to expect good results. In this research, we proposed a new approach within the Dynamical Mean Field Theory (DMFT) framework that requires a simpler and potentially less numerical-cost algorithm. We implemented this algorithm by constructing the local self-energy matrix elements that depend on the occupancy fluctuations. We integrated them over all possible occupancy configurations to obtain the fully interacting Green functions. The resulted Green function matrix was then used to compute the density of states (DOS) and other quantities. We investigated the case of quarter filling. Our computation results showed that pseudogap appeared when the onsite Coulomb repulsion was sufficiently high and tended to diminish as temperature increased. The system preserved its paramagnetic metallic character for all circumstances we studied.