Origin of the Peak-Dip-Hump Line Shape in the Superconducting-State $(\pi ,0)$ Photoemission Spectra of ${\mathrm{B}\mathrm{i}}_2{\mathrm{S}\mathrm{r}}_2{\mathrm{C}\mathrm{a}\mathrm{C}\mathrm{u}}_2{\mathrm{O}}_8$

From detailed high-resolution measurements of the photon energy dependence of the $(\pi ,0)$ superconducting-state photoemission spectrum of the bilayer Bi high-temperature superconductors, we show that the famous peak-dip-hump line shape is dominated by a superposition of spectral features originating from different electronic states which reside at different binding energies, but are each describable by essentially identical single-particle spectral functions. The previously identified bilayer-split ${\mathrm{C}\mathrm{u}\mathrm{O}}_2$ bands are the culprit: with the ”superconducting” peak being due to the antibonding band, while the hump is mainly formed by its bonding bilayer-split counterpart.