Two characteristic energies in the low-energy magnetic response of the electron-doped high-temperature superconductor Nd2-xCexCuO4+delta

Abstract

Neutron scattering for Nd2−xCexCuO4+delta (x~0.155, Tc=25 K) reveals two distinct magnetic energy scales in the superconducting state: omega1~6.4 meV and omega2~4.5 meV. These magnetic energies agree quantitatively with the B1g /B2g and A1g features observed in electronic Raman scattering, where the former is believed to indicate the maximum superconducting gap and the origin of the latter has remained unexplained. The data are inconsistent with previous claims of the existence of a magnetic resonance mode near 10 meV, but consistent with a resonance at omega2 and with the recently established universal ratio of resonance energy to superconducting gap in unconventional superconductors.