Resonance in Optimally Electron-Doped Superconductor Nd$_{1.85}$Ce$_{0.15}$CuO$_{4-\delta}$

TL;DR

This study uses neutron scattering to reveal a magnetic resonance in an electron-doped cuprate superconductor, suggesting a universal feature linked to high-temperature superconductivity.

Contribution

It demonstrates the presence of a resonance in electron-doped cuprates, similar to hole-doped ones, indicating a common mechanism in high-$T_c$ superconductivity.

Findings

Resonance appears at the antiferromagnetic wavevector ${f Q}=(1/2,1/2,0)$.

Resonance intensity correlates with the superconducting order parameter.

A spin pseudogap opens above the resonance energy.

Abstract

We use inelastic neutron scattering to probe magnetic excitations of an optimally electron-doped superconductor Nd$_{1.85}$Ce$_{0.15}$CuO$_{4-\delta}$ 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 ${\bf Q}=(1/2,1/2,0)$, the effect of superconductivity is to form a resonance centered also at ${\bf Q}=(1/2,1/2,0)$ 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.