Various experimental and theoretical findings suggests the effect of next-nearest-neighbor (NNN) hopping amplitude t' on the physical properties of the cuprates. The magnitude of t' is found to be material dependent and is different for different materials. moreover the sign of t' is different for electron and hole doped cuprates.But what is the range of magnitude of t'? More specifically what regime of t' is associated with high Tc cuprates? What is the maximum values of t' in both electron and hole doped material respectively? To, which compound they are associated with?
There is a nice article by Hanke and his coworkers in Low Temperature Physics, 32, 457 (2006). They have done a numerical study of the doping dependence of the spectral function of the n-type cuprates. Using a variational cluster-perturbation theory approach based upon the self-energy-functional theory, the spectral function of the electron-doped two-dimensional Hubbard model is calculated. The model includes the next-nearest-neighbor electronic hopping amplitude t′ and a fixed on-site interaction U = 8t at half-filling and doping levels ranging from x = 0.077 to x = 0.20. Their results support the fact that a comprehensive description of the single-particle spectrum of electron-doped cuprates requires a proper treatment of strong electronic correlations. In contrast to previous weak-coupling approaches, they obtain a consistent description of the ARPES experiments without the need to (artificially) introduce a doping-dependent on-site interaction U.
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