In this paper we study the ground state phase diagram of a one-dimensional t-J-U model away from half-filling. In the large-bandwidth limit and for ferromagnetic exchange with easy-plane anisotropy a phase with gapless charge and massive spin excitations, characterized by the coexistence of...

We employ density-functional theory to calculate realistic parameters for an extended Hubbard model of the molecular metal TTF-TCNQ. Considering both intra- and intermolecular screening in the crystal, we confirm the importance of the suspected longer-range Coulomb interactions along the...

The long-range forces between holes in an antiferromagnet are due to magnon exchange. The one-magnon exchange potential between two holes is proportional to cos(2 ϕ)/<Emphasis Type="Bold">r <Superscript>2</Superscript> where <Emphasis Type="Bold">r is the distance vector of the holes and ϕ is the angle between <Emphasis Type="Bold">r and an axis of the square crystal lattice....</emphasis></emphasis></superscript></emphasis>