Two characteristic energies in the low-energy antiferromagnetic response of the electron-doped high-temperature superconductor Nd${}_{2-x}$Ce${}_x$CuO${}_{4+\delta }$

Abstract

Inelastic neutron scattering for Nd${}_{2-x}$Ce${}_x$CuO${}_{4+\delta }$ near optimal doping ($x\approx 0.155$, $T_c=25\mathrm{K}$) reveals that the dynamic magnetic susceptibility at the antiferromagnetic zone center exhibits two characteristic energies in the superconducting state: ${\omega }_1\approx 6.4\mathrm{meV}$ and ${\omega }_2\approx 4.5\mathrm{meV}$. These two magnetic energies agree $quantitatively$ with the $B_{1g}$ / $B_{2g}$ and $A_{1g}$ features previously observed in electronic Raman scattering, where the former is believed to indicate the maximum electronic gap and the origin of the smaller $A_{1g}$ feature has remained unexplained. The susceptibility change upon cooling into the superconducting state is inconsistent with previous claims of the existence of a magnetic resonance mode near 10 meV, but consistent with a resonance at ${\omega }_2$.

5 pages, 3 figures