Role of inter-site Coulomb interaction on the thermodynamic and ground state properties within the t - J - U - V model

In this work, we report the effect of nearest neighbor (NN) inter-site Coulomb interaction (V) with a certain finite value of on-site Coulomb repulsion (U) and NN antiferromagnetic exchange interaction (J) in the context of high-T-c cuprates. An exact diagonalization method has been applied in a 2D t-J-U model extended by NN inter-site Coulomb interaction in the tilted square cluster near optimal doping. The antiferromagnetic tendency is suppressed by the inter-site e - e repulsion. The inter-site Coulomb repulsion produces an effective on-site attraction between electrons, resulting in the creation of doublons against the on-site Coulomb repulsion. The computation of binding energy demonstrates the binding of holes for small U/t, resulting from the interplay between U and V. Superconductivity arises in a limited window of V depending on U. However, the effective dominance of either U or V results in the annihilation of these hole pairs. The presence of two peaks in specific heat is caused by two Coulomb interactions. The development of doublons as V increases leads to a more ordered state, lowering entropy. The thermodynamic properties also show that the t - J - U - V model acts as an attractive Hubbard model for U < V. However, a pure attractive t - J - U model cannot explain these phenomenologies.