Many-body interactions in hole-doped high-Tc cuprates studied by high-resolution ARPES

We have performed high-resolution angle-resolved photoemission spectroscopy on hole-doped high-Tc cuprate superconductors (HTSCs) to study many-body interaction and the universality of low-energy excitation gap. In Bi2Sr2CaCu2O8 (Bi2212), we observed a kink in the dispersion in the off-nodal region in the superconducting state, which remarkably weakens on impurity substitution. We also find that the appearance of the kink in the off-nodal region is a common feature of Bi2212 and La1.85Sr0.15CuO4 (LSCO), while the energy scale is remarkably different between two compounds (70 and 20 meV). We discuss universality of the kink in dispersion in the hole-doped HTSCs in terms of the coupling of electrons with spin fluctuations.