High-T_c Superconductivity within t - t'- J - J' Model

The behaviour of high-T_c cuprates in its ground state has been examined within the t-t'-J-J' model using an exact method. The role of next-nearest-neighbor (NNN) hopping (t') and exchange (J') interactions on the charge gap, spin gap and effective exchange interaction has been investigated. Charge gap shows a gapped behavior. Spin gap curves establish a gapless behavior at small t'/t and J'/t. Also, it appears that effective exchange interaction is very much relevant in the present system