Why is the ARPES anti-nodal singularity at 40 meV shifted in superconducting state of HTSC, but the kink at 70 meV is not?

TL;DR

This paper presents a theoretical model explaining why the ARPES anti-nodal singularity shifts in the superconducting state of HTSC, while the 70 meV kink remains unchanged, highlighting the role of electron-phonon interactions.

Contribution

The model introduces a forward scattering peak in electron-phonon interaction to explain ARPES features in HTSC, including the differential shift of spectral singularities.

Findings

The model reproduces the ARPES observed kink at 70 meV in the normal state.

It explains the shift of the 40 meV anti-nodal singularity in the superconducting state.

Predicts a dip-hump structure consistent with ARPES data.

Abstract

The theoretical model for the quasiparticle self-energy in HTSC is proposed, which is based on the forward scattering peak in the electron-phonon (EPI) interaction. By assuming that EPI dominates, the model explains qualitatively and in a consistent way the recent ARPES results. The latter show a kink in the normal state quasiparticle energy at 70 meV in the nodal direction, which is (surprisingly) not shifted in the superconducting (SC) state, while the singularity at 40 meV in the anti-nodal direction is shifted by the SC gap. The model predicts a dip-hump structure in the spectral function, which is observed in ARPES.