Direct spectroscopic evidence for phase competition between the pseudogap and superconductivity in Bi₂Sr₂CaCu₂O_8+δ

In the high-temperature (T_c) cuprate superconductors, a growing body of evidence suggests that the pseudogap phase, existing below the pseudogap temperature T∗, is characterized by some broken electronic symmetries distinct from those associated with superconductivity. In particular, recent scattering experiments have suggested that charge ordering competes with superconductivity. 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 Bi₂Sr₂CaCu₂O_8+δ as compelling evidence for phase competition, which persists up to a high hole concentration p ∼ 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.