Phys Rev Lett. 2008 Oct 31;101(18):187001. doi: 10.1103/PhysRevLett.101.187001. Epub 2008 Oct 27.

Feedback spin resonance in superconducting CeCu2Si2 and CeCoIn5.

Physical review letters

I Eremin, G Zwicknagl, P Thalmeier, P Fulde

PMID: 18999854 DOI: 10.1103/PhysRevLett.101.187001

Abstract

We show that the recently observed spin resonance modes in heavy-fermion superconductors CeCoIn5 and CeCu2Si2 are magnetic excitons originating from superconducting quasiparticles. The wave vector Q of the resonance state leads to a powerful criterion for the symmetry and node positions of the unconventional gap function. The detailed analysis of the superconducting feedback on magnetic excitations reveals that the symmetry of the superconducting gap corresponds to a singlet d_{x;{2}-y;{2}} state symmetry in both compounds. In particular this resolves the long-standing ambiguity of the gap symmetry in CeCoIn5. We demonstrate that in both superconductors the resonance peak shows a significant dispersion away from Q which can be checked experimentally. Our analysis reveals the similar origin of the resonance peaks in the two heavy-fermion superconductors and in layered cuprates.

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• Journal Article