Nonmonotonic d_<x^2-y^2>-Wave Superconductivity in Electron-Doped Cuprates Viewed from the Strong-Coupling Side(Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties)

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Applying a variational Monte Carlo method to a two-dimensional t-J model, we study the nonmonotonic d_<x^2-y^2>-wave superconductivity observed by Raman scattering and angle-resolved photoelectron spectroscopy experiments in electron-doped cuprates. As a gap function in the trial state, we extend the d-wave form (ext.d) so as to have its maxima located near hot spots of the system. It is found that the ext.d wave is always more stable than the simple d wave in the electron-doped case, and the magnetic correlation of the wave vector (π, π) as well as the pair correlation is enhanced. These results corroborate spin-correlation-mediated superconductivity in cuprates, which was recently argued from a FLEX calculation. In addition, we confirm that s- and p-wave symmetries are never stabilized even in an overdoped regime.
2005-07-15