On effect of Van Hove root singularity on critical temperature of high-temperature superconductors

It is shown, that the Van Hove root singularity in ν (EF) ∼ (EF - E0)-1/2 state density, linked with extended saddle features in the electron spectrum of high-temperature superconductors based on cuprate metal-oxide hole-type compounds, leads to a non-monotonous dependence of the critical temperature Tc on the position of the Fermi level EF relative to the saddle bottom E0. Dependence of Tc on the hole concentration, obtained in a strong coupling approximation, agrees qualitatively with experimental data for re-doped cuprate metal-oxides