Bulk electronic structures and strong electron–phonon interactions in an electron-doped high-temperature superconductor

Abstract

We have performed soft x-ray angle-resolved photoemission spectroscopy (ARPES) for the electron-doped high-temperature superconducting cuprates (HTSCs) Nd2-xCexCuO4 (x=0.075 and 0.15) in order to disclose their genuine bulk electronic structures. Our soft x-ray ARPES has revealed that the bulk-derived nodal ‘kink’ (the abrupt change of the electron velocity in quasiparticle dispersions), being absent in the low-energy ARPES, is clearly observable for the electron-doped superconducting Nd1.85Ce0.15CuO4. This result confirms that the antiferromagnetic spin correlation is suppressed and the electron–phonon interactions are prevailing in the bulk of the electron-doped superconducting Nd2- xCexCuO4 at the optimal doping level. The nodal ‘kink’ behavior is equivalent to that observed in the hole-doped HTSCs. The anisotropic strong electron–phonon interactions seem to be inherent in the HTSCs irrespective of the type of doped carriers.