Quasiparticle resonance states induced by a nonmagnetic impurity in Gossamer superconductors

The local density of states (LDOS) around a nonmagnetic impurity in Gossamer superconductors has been studied based on the two-dimensional t-U-J model. Within the Gutzwiller projected mean-field approximation and Bogoliubov-de Gennes theory, the order parameters are determined in a self-consistent way, and the main related experimental results are reproduced. In the large U limit without electron double occupancy, the impurity induced quasiparticle resonance states appear at low energies, at the same time the asymmetric superconducting coherence peaks are strongly suppressed. With increasing double occupancy number d which is modulated by the Coulomb repulsion U, the order parameter gradually decreases, while the impurity induced resonance states always survive, then move to the Fermi energy and merge into a single resonance peak when the double occupancy d is big enough. These features mean for different superconducting compounds with or without strong electron correlation, the impurity induced resonance states may vary, strongly suggesting the role played by the electron correlation in cuprate superconductors.