Resonance in Optimally Electron-Doped Superconductor Nd 1.85 Ce 0.15 CuO 4−δ
Jun Zhao, Pengcheng Dai, Shiliang Li, Paul G. Freeman, Y. Onose, Y. Tokura
Abstract
We use inelastic neutron scattering to probe magnetic excitations of an optimally electron-doped superconductor Nd
1.85
Ce
0.15
CuO
4−δ
above and below its superconducting transition temperature
T
c
=25
K. In addition to gradually opening a spin pseudo gap at the antiferromagnetic ordering wavevector
Q=(1/2,1/2,0)
, the effect of superconductivity is to form a resonance centered also at
Q=(1/2,1/2,0)
but at energies above the spin pseudo gap. The intensity of the resonance develops like a superconducting order parameter, similar to those for hole-doped superconductors and electron-doped Pr
0.88
LaCe
0.12
CuO
4
. The resonance is therefore a general phenomenon of cuprate superconductors, and must be fundamental to the mechanism of high-
T
c
superconductivity.