This study presents evidence for strong electron-phonon coupling in high-temperature superconductors (HTS). Using angle-resolved photoemission spectroscopy (ARPES), the researchers investigated electron dynamics in three families of copper oxide superconductors: Bi2212, Pb-Bi2212, and LSCO. They observed an abrupt change in electron velocity at 50-80 meV, which they attribute to coupling with oxygen-related phonons. This suggests that electron-phonon coupling strongly influences electron dynamics in HTS and must be included in any microscopic theory of superconductivity. The study also compares ARPES data with neutron scattering data on LSCO, finding strong support for the phonon interpretation. The energy of the zone boundary in-plane oxygen stretching longitudinal optical (LO) phonon matches the "kink" energy in the data, indicating a strong coupling between the phonon and charge. The data also show that the kink persists above the transition temperature, consistent with electron-phonon coupling. The study rules out the magnetic mode as the origin of the "kink" and "dip" features, as these are not observed in systems without magnetic modes. The phonon interpretation is further supported by the similarity between ARPES data and known phonon cases, as well as the temperature dependence of the kink. The study also shows that the velocity ratio changes with doping and angle, consistent with phonon coupling. The study concludes that phonons are the most plausible explanation for the observed phenomena, despite some alternative interpretations. The findings suggest that electron-phonon coupling is a key factor in the behavior of HTS, and further theoretical work is needed to fully understand the role of phonons in superconductivity.This study presents evidence for strong electron-phonon coupling in high-temperature superconductors (HTS). Using angle-resolved photoemission spectroscopy (ARPES), the researchers investigated electron dynamics in three families of copper oxide superconductors: Bi2212, Pb-Bi2212, and LSCO. They observed an abrupt change in electron velocity at 50-80 meV, which they attribute to coupling with oxygen-related phonons. This suggests that electron-phonon coupling strongly influences electron dynamics in HTS and must be included in any microscopic theory of superconductivity. The study also compares ARPES data with neutron scattering data on LSCO, finding strong support for the phonon interpretation. The energy of the zone boundary in-plane oxygen stretching longitudinal optical (LO) phonon matches the "kink" energy in the data, indicating a strong coupling between the phonon and charge. The data also show that the kink persists above the transition temperature, consistent with electron-phonon coupling. The study rules out the magnetic mode as the origin of the "kink" and "dip" features, as these are not observed in systems without magnetic modes. The phonon interpretation is further supported by the similarity between ARPES data and known phonon cases, as well as the temperature dependence of the kink. The study also shows that the velocity ratio changes with doping and angle, consistent with phonon coupling. The study concludes that phonons are the most plausible explanation for the observed phenomena, despite some alternative interpretations. The findings suggest that electron-phonon coupling is a key factor in the behavior of HTS, and further theoretical work is needed to fully understand the role of phonons in superconductivity.