Momentum, temperature, and doping dependence of photoemission lineshape and implications for the nature of the pairing potential in high-T-c superconducting materials

The anomalous momentum and temperature dependence of the spectral lineshape in data from underdoped Bi2Sr2CaCu2O8+delta (Bi2212) indicates that the quasiparticles are strongly coupled to collective excitations centered near Q = (pi, pi). The doping dependence of the spectral lineshape and its correlation with the size of the superconducting gap indicate these collective excitations are related to the pairing interaction in high-T-c superconductors, in analogy with phonon induced structures in tunneling spectra of low T-c materials.