Direct spectroscopic evidence for phase competition between the pseudogap and superconductivity in Bi2Sr2CaCu2O8+delta

In the high-temperature (T-c) cuprate superconductors, a growing body of evidence suggests that the pseudogap phase(1), existing below the pseudogap temperature T*, is characterized by some broken electronic symmetries distinct from those associated with superconductivity(2-21). In particular, recent scattering experiments have suggested that charge ordering competes with superconductivity(18-21). However, no direct link of an interplay between the two phases has been identified from the important low-energy excitations. Here, we report an antagonistic singularity at T-c in the spectral weight of Bi2Sr2CaCu2O8+delta as compelling evidence for phase competition, which persists up to a high hole concentration p similar to 0.22. Comparison with theoretical calculations confirms that the singularity is a signature of competition between the order parameters for the pseudogap and superconductivity. The observation of the spectroscopic singularity at finite temperatures over a wide doping range provides new insights into the nature of the competitive interplay between the two orders and the complex phase diagram near the pseudogap critical point.