Universal waterfall-like feature in the spectral function of high temperature superconductors

By performing high resolution angle resolved photoemission spectroscopy (ARPES) experiments on four different families of p-type cuprates, over an energy range much bigger than investigated before, we report the discovery of a universal high energy anomaly in the spectral function. This anomaly is characterized by the presence of two new high energy scales E1 = 0.35–0.45 eV and E2 = 0.8–0.9 eV and the pinning of the main ARPES spectral function along the boundary of a diamond in the momentum space. This anomaly unveils a missing link between the doped oxygen holes and the quasiparticles, providing a full range of relevant interactions to the high Tc problem.