1. Element-specific probe of quantum criticality in $\mathrm{CeCoIn_{5}}$
- Author
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Khansili, A., Sharma, R., Hissariya, R., Baev, I., Schwarz, J., Kielgast, F., Nissen, M., Martins, M., Huang, M. -J., Hoesch, M., Paidi, V. K., van Lierop, J., Rydh, A., and Mishra, S. K.
- Subjects
Condensed Matter - Strongly Correlated Electrons ,Condensed Matter - Superconductivity - Abstract
Employing the elemental sensitivity of x-ray absorption spectroscopy (XAS) and x-ray magnetic circular dichroism (XMCD), we study the valence and magnetic order in the heavy fermion superconductor CeCoIn$_5$. We probe spin population of the f-electrons in Ce and d-electrons in Co as a function of temperature (down to 0.1 K) and magnetic field (up to 6 T). From the XAS we find a pronounced contribution of Ce$^{4+}$ component at low temperature and a clear temperature dependence of the Ce valence below 5 K, suggesting enhanced valence fluctuations, an indication for the presence of a nearby quantum critical point (QCP). We observe no significant corresponding change with magnetic field. The XMCD displays a weak signal for Ce becoming clear only at 6 T. This splitting of the Kramers doublet ground state of Ce$^{3+}$ is significantly smaller than expected for independent but screened ions, indicating strong antiferromagnetic pair interactions. The unconventional character of superconductivity in CeCoIn$_5$ is evident in the extremely large specific heat step at the superconducting transition., Comment: 5 pages, 5 figures. Supplementary information (4 pages, 5 figures)
- Published
- 2022