Competition between the pseudogap and superconductivity and its critical point*

In high-temperature cuprate superconductors, the nature of the pseudogap remains unresolved. Recently, there have been increasing evidence that the pseudogap is a distinct order from superconductivity, but it has not been completely understood how the pseudogap affects the superconductivity. To reveal the interplay between the pseudogap and superconductivity, we have performed ARPES measurement on a wide doping range of Bi2212. From the analysis of the spectral weight, we found a singular behavior at Tc at the antinode, indicating the competition between the order parameters for the pseudogap and superconductivity. This signature for the competition at Tc becomes weaker with hole doping, and disappears at $\sim$22\% hole doping. Together with spectroscopic evidence for the ground-state critical point at 19\%, our result reveals the non-trivial termination of the interplay between the pseudogap and superconductivity.