Thermodynamic properties of small extended Hubbard rings

We have obtained the exact numerical results of the specific heat, the susceptibility and the correlation functions L0(T) and L1(T) for finite extended Hubbard rings at the large U limit. It is shown that the nearest neighbor interactions favor the ferromagnetic ordering. When the number of electrons is less than the number of sites, the electron hopping results in itinerant magnetism and washes out the high temperature peak (around T = U/kB) in the specific heat. In all cases, the behaviors of L0(T) and L1(T) are consistent with the characteristic features of the specific heat and the susceptibility. Thd exact results are used to test the accuracy of the Roth's decoupling scheme.