Dominance of the electron-phonon interaction with forward scattering peak in high- Tc superconductors: Theoretical explanation of the ARPES kink

The angle-resolved photoelectron spectroscopy (ARPES) spectra in high- T_c superconductors show four distinctive features in the quasiparticle self-energy Σ(k,ω) . They can be explained consistently by the phenomenological microscopic theory in which the electron-phonon interaction with the forward-scattering peak dominates over the Coulomb scattering. This theory explains why there is no shift of the nodal kink at 70meV in the superconducting state, contrary to the observed shift of the antinodal singularity at 40meV . The theory predicts a kneelike structure of ∣ImΣ(ω)∣=∣ImΣ_ph(ω)+ImΣ^C(ω)∣ , which is phonon dominated, ∣ImΣ(ω_ph)∣≈∣ImΣ_ph(ω_ph)∣∼πλ_phω_ph/2 , for ω≈ω_ph⁽⁷⁰⁾ , and for ω>ω_ph⁽⁷⁰⁾ shows linear behavior ∣ImΣ(ω)∣≈∣ImΣ_ph(ω_ph)∣+πλ_C,φω/2 , due to the Coulomb scattering. ARPES spectra give λ_ph>1 —which is obtained from ReΣ , and λ_C<0.4 —obtained from ImΣ , i.e., λ_ph≫λ_C . The dip-hump structure in the spectral function A(k_F,ω) comes out naturally from the proposed theory.