Exact thermodynamics of an extended Hubbard model of single and paired carriers in competition

By exploiting the technique of Sutherland’s species, introduced in Phys. Rev. B $63,$ 121103, we derive the exact spectrum and partition function of a one-dimensional extended Hubbard model. The model describes a competition between dynamics of single carriers and short-radius pairs, as a function of on-site Coulomb repulsion (U) and filling $\left(\rho \right).\mathrm{}$ We provide the temperature dependence of the chemical potential, compressibility, local magnetic moment, and specific heat. In particular the latter turns out to exhibit two peaks, both related to “charge” degrees of freedom. Their origin and behavior are analyzed in terms of kinetic and potential energy, both across the metal-insulator transition point and in the strong-coupling regime.