We show that the double kink-structure in the electronic self-energy of Bi2212 near the nodal point at low energy $\omega_{ 1}\approx 50-70$ $meV$ and at high energy at $\omega_{ 2}\approx 350$ $meV$, observed recently in the ARPES measurements by Valla et al \cite{ Valla-2006}, gives that the electron-phonon (EPI) coupling constant $\lambda_{ z}^{ EP}$in the normal part of the self-energy $\Sigma (\omega)$ is twice larger than the Coulomb coupling $\lambda_{ z}^{ C}$. The experimental data for $\func{ Re}\Sigma (\omega)$ up to energies $\sim 350$ $meV$ can be satisfactory explained by $% \lambda_{ z}^{ EP}\approx 2.1$ and $\lambda_{ z}^{ C}\approx 1.1$. Additionally the low energy slope of the ARPES $\func{ Re}\Sigma (\omega)$ at $\omega <20$ $meV$ \cite{ Valla-2006} gives a hint that the low energy phonons might contribute significantly to the EPI coupling, i.e. $\lambda_{ z}^{ low,EP}>1$, thus giving the total EPI coupling constant $\lambda_{ z,tot}^{ EP}=\lambda_{ z}^{ EP}+\lambda_{ z}^{ low,EP}>3$. In order to test the role of low frequency phonons by ARPES measurements a much better momentum resolution is needed than that reported in \cite{ Valla-2006}. Possible pairing scenarios based on ARPES, tunnelling and magnetic neutron scattering measurements are discussed.
Categories: cond-mat.supr-con cond-mat.str-el