Spin resonance in the d-wave superconductor CeCoIn5

TL;DR

This study uses neutron scattering to investigate antiferromagnetic spin fluctuations and a spin resonance in the d-wave superconductor CeCoIn$_{5}$, revealing strong coupling between magnetism and superconductivity.

Contribution

It provides the first detailed characterization of spin fluctuations and resonance in CeCoIn$_{5}$, highlighting their role in its unconventional superconductivity.

Findings

Superconductivity emerges from a state with slow, commensurate antiferromagnetic fluctuations.

A sharp spin resonance appears below T_c at 0.60 meV, indicating strong magnetism-superconductivity coupling.

The resonance supports a d-wave gap symmetry with sign change across the wavevector Q_0.

Abstract

Neutron scattering is used to probe antiferromagnetic spin fluctuations in the d-wave heavy fermion superconductor CeCoIn$_{5}$ (T$_{c}$=2.3 K). Superconductivity develops from a state with slow ($\hbar\Gamma$=0.3 $\pm$ 0.15 meV) commensurate (${\bf{Q_0}}$=(1/2,1/2,1/2)) antiferromagnetic spin fluctuations and nearly isotropic spin correlations. The characteristic wavevector in CeCoIn$_{5}$ is the same as CeIn$_{3}$ but differs from the incommensurate wavevector measured in antiferromagnetically ordered CeRhIn$_{5}$. A sharp spin resonance ($\hbar\Gamma<0.07$ meV) at $\hbar \omega$ = 0.60 $\pm$ 0.03 meV develops in the superconducting state removing spectral weight from low-energy transfers. The presence of a resonance peak is indicative of strong coupling between f-electron magnetism and superconductivity and consistent with a d-wave gap order parameter satisfying $\Delta({\bf q+Q_0})=-\Delta({\bf q})$.