Coexistence of both coherent and incoherent peaks in photoemission spectra of intermediately correlated many-electron systems

We have theoretically studied various one-, two- and three-dimensional half-filled Hubbard models from weak correlation cases to strong ones, and calculated the Lehmann's spectra of the momentum-specified one-electron Green's functions, as well as the total density of states (DOS), using the quantum Monte-Carlo method. In the region of intermediate correlation strength, we have found the DOS has new characteristic peaks near the Fermi level, in addition to the well-known upper and lower Hubbard-band peaks. We show these new peaks near the Fermi level comes from quasi-coherent states, while the upper and lower Hubbard-band peaks comes from strongly incoherent ones. This multi-peaked structure, appearing only in the intermediate region, is shown to be quite insensitive to the dimensionality. Finally, we compare our results with the static single impurity model, and give a rough and intuitive explanation for the origin of this newly obtained multi-peaked structure. Our results also qualitatively agree with the recent photoemission experiments on CaVO3 and SrVO3 crystals