Anomalous temperature dependence in the photoemission spectral function of cuprates

Temperature-dependent angle-resolved photoemission experiments were performed on overdoped single layer Bi2Sr2CuO6 (T(c)similar to4 K) and on the parent compounds Sr2CuO2Cl2 and Ca2CuO2Cl2. Contrary to the more conventional results obtained on Bi2Sr2CuO6, the parent compounds show strong temperature dependence over a wide energy range that is two orders of magnitude larger than the temperature scale involved. The doping dependence strongly suggests that the anomalous temperature dependence has its origin in the novel many-body physics in the Mott insulators. We consider the observed temperature dependence using a heuristic model with multiple initial and final states in the photoemission process. The nature of the multiple states and broad photoemission line shape in parent compounds is also given.