Fine structure in the tunneling spectra of electron-doped cuprates: No coupling to magnetic resonance mode

We analyze high-resolution scanning tunneling spectra of the electron-doped cuprate Pr0.88LaCe0.12CuO4 (T_c = 24 K). We find that the spectral fine structure below 35 meV is consistent with strong coupling to a bosonic mode at 16 meV, in quantitative agreement with early tunneling spectra of Nd1.85Ce0.15CuO4. Since the energy of the bosonic mode is significantly higher than that (9.5-11 meV) of the magnetic resonance-like mode observed by inelastic neutron scattering, the coupling feature at 16 meV cannot arise from strong coupling to the magnetic mode. The present work thus demonstrates that the magnetic resonance-like mode cannot be the origin of high-temperature superconductivity in electron-doped cuprates.