Abstract
The effects of next-nearest-neighbor (t ′ ) and third-nearest-neighbor (t ″ ) hopping terms on superconductivity correlation in two-dimensional extended t-J model were investigated. The presence of t ′ was found to be important for enhancing pairing beyond underdoped regime using variational approach supplemented by slave-boson mean-field (MF) calculations. It was observed that d-wave superconductivity correlation was slightly suppressed by t ′ and t ″ in underdoped regions which was enhanced in optimal and overdoped regions. The results show that the Fermi surface changes from holelike to electronlike once maximum pairing is reached.