Charge Orderings and Phase Separations in Itinerant Fermion Systems at Half Filling
W.R. Czart, P.R. Grzybowski, M. Nogala and S. Robaszkiewicz
Faculty of Physics, A. Mickiewicz University, Umultowska 85, 61-614 Poznań, Poland
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We analyse the ground state phase diagrams of the charge orderings in narrow band materials using two effective models: (1) the spinless fermion model (t-W) with repulsive intersite interaction (Wij > 0) and (2) the molecular crystal model with the coupling of electrons to intramolecular (crystal field) vibrations. We present results for the case of half filled bands for d = 2 square lattice. The calculations are performed within the (broken symmetry) Hartree-Fock approximation. The study takes into consideration the effects of frustrating next-nearest-neighbour hopping (t2) on the charge ordered states in these systems. We focus on the two cases: (i) homogeneous phases and phase separations involving checkerboard charge ordering with the nesting vector Q= (π, π) only and (ii) homogeneous phases and phase separations involving two types of charge ordering: (a) checkerboard charge ordering with the nesting vector Q = (π, π), and (b) collinear (CL) charge ordering with Q = (0, π) or Q = (π, 0).
DOI: 10.12693/APhysPolA.121.1042
PACS numbers: 71.10.Fd, 71.30.+h, 71.45.Lr, 64.75.Gh