New interpretation of the doping and temperature dependence of photoemission lineshape and its implication to the high Tc superconductivity.

Recent findings in the experiments on high T-c superconductors by angle resolved photoemission are discussed. Detailed temperature and doping dependent lineshape studies on cuprates lead to a new interpretation of the photoemission data. The broad photoemission peaks which often extend to the Fermi level when they are a few hundred meV away from the Fermi level are not single states with very large broadening. Rather, the broad structure should be interpreted as a collection of states. It is found that the low energy part of this structure is involved in the pairing and, contrary to the conventional superconductors, the pairing occurs not only near the so called Fermi surface but also away from it.