We present a detailed study of the ground state and low-temperature properties of the integrable Hubbard model with bond-charge interaction, including its conducting properties and scaling behavior near the U-driven quantum phase transitions. Remarkably, the model displays fractional statistical properties, which enlighten the nature of various physical properties, such as the fractional elementary excitations, and give rise to a disordered condensate and phase separation in k space, as well as to a topological change in the generalized Fermi surface at half filling.

No abstract

No abstract

We show that the Hubbard model with infinite-range Coulomb coupling is equivalent to an ideal gas of three species of particles obeying fractional exclusion statistics. A full appreciation of this mapping requires an extension of the pertinent formalism. This very simple, but rather peculiar model is exactly solvable in any dimension and exhibits a Mott metal-insulator transition, whose universality class is shown to be that of a free spinless Fermi gas. A modified version of the Luttinger theorem is shown to apply in any dimension. We also characterize the metallic and insulating phases by obtaining the electronic band structure as well as the interacting density of states. The fractional statistics manifests itself on the amplitudes of several thermodynamic quantities and, in particular, the Pauli spin susceptibility is subdominant in all metallic phases, and a Curie-type of response appears.

We investigate the ground-state and low-temperature properties of the integrable version of the PensonKolb-Hubbard chain. The model obeys fractional statistical properties, which give rise to fractional elementary excitations and manifest differently in the four regions of the phase diagram U / t versus n, where U is the Coulomb coupling, t is the correlated hopping amplitude, and n is the particle density. In fact, we can find local pair formation, fractionalization of the average occupation number per orbital k, or U-and n-dependent average electric charge per orbital k. We also study the scaling behavior near the U-driven quantum phase transitions and characterize their universality classes. Finally, it is shown that in the regime of parameters where local pair formation is energetically more favorable, the ground state exhibits power-law superconductivity; we also stress that above half filling the pair-hopping term stabilizes local Cooper pairs in the repulsive-U regime for U Ͻ U c1 =−2t cos͑n / 2͒.