Specific heat, entropy and magnetic properties of high Tc superconductivity within the planar t−t′−J−V model

The finite temperature properties of the high Tc cuprates are investigated by an exact method at optimal doping using t−t′−J−V model. The role of next-nearest-neighbor (NNN) hopping interaction t′ and nearest-neighbor Coulomb repulsion V on the total energy, specific heat, entropy, magnetic properties, etc. in the superconducting, as well as normal phase, are considered. Specific heat curves show a single peak structure in the parameter range suitable for existence of superconducting phase. Two peak structure in the specific heat curve is observed at sufficiently large values of V∕t. An asymmetry in specific heat curves and peak positions is observed for the hole- and electron-doped cuprates. Existence of a metallic phase is detected for positive t′∕t for V∕t ≤ 4J. Entropy calculation shows the system goes to a more disordered state with negative t′∕t and V∕t. A non-Fermi liquid behavior is revealed at low temperatures for positive t′ and small values of V . An asymmetry in Neel temperature is observed for the hole- and electron-doped cuprates. An unsaturated ferromagnetic phase emerges with an increase of V∕t. Schematic magnetic phase diagrams are shown. Graphical abstract