Electronic structure and $f$ -orbital occupancy in Yb-substituted CeCoIn ${}_5$

Journal Article · Wed Jun 01 04:00:00 EDT 2011 · Physical Review. B, Condensed Matter and Materials Physics

DOI:https://doi.org/10.1103/PhysRevB.83.235117· OSTI ID:1052161

Booth, C. H.; Durakiewicz, T.; Capan, C.; Hurt, D.; Bianchi, A. D.; Joyce, J. J.; Fisk, Z.

The local structure and 4f orbital occupancy have been investigated in Ce_1-xYb_xCoIn₅ via Yb L_III-edge extended x-ray absorption fine structure (EXAFS), Ce and Yb L_III-edge x-ray absorption near-edge structure (XANES), and angle-resolved photoemission spectroscopy (ARPES) measurements. Yb(III) (4f¹³) is the hole analog of Ce(III) (4f¹). Yb is found to be strongly intermediate-valent in Ce_1-xYb_xCoIn₅ throughout the entire doping range, including pure YbCoIn5, with an f-hole occupancy for Yb of n_f≃0.3 (i.e., Yb^2.3+), independent of Yb concentration and independent of temperature down to T=20 K. In contrast, the f-electron orbital occupancy for Ce remains close to 1 for all Yb concentrations, suggesting that there is no mutual influence on n_f between neighboring Ce and Yb sites. Likewise, ARPES measurements at 12 K have found that the electronic structure along Γ-X is not sensitive to the Yb substitution, suggesting that the Kondo hybridization of Ce f electrons with the conduction band is not affected by the presence of Yb impurities in the lattice. The emerging picture is that in Ce_1-xYb_xCoIn₅ there are two networks, interlaced but independent, that couple to the conduction band: one network of Ce ions in the heavy-fermion limit, and one network of Yb ions in the strongly intermediate-valent limit. Finally, the robustness of the local and electronic structure to doping suggests the absence of charge transfer between the Ce and Yb ions, and may explain the relative robustness of superconductivity for this Ce-site substitution as compared to the In-site substitution.

• Research Organization: Ernest Orlando Lawrence Berkeley National Laboratory, Berkeley, CA (US)
• Sponsoring Organization: Chemical Sciences Division
• DOE Contract Number: AC02-05CH11231
• OSTI ID: 1052161
• Report Number(s): LBNL-5211E
• Journal Information: Physical Review. B, Condensed Matter and Materials Physics, Journal Name: Physical Review. B, Condensed Matter and Materials Physics Journal Issue: 23 Vol. 83; ISSN 1098-0121; ISSN PRBMDO
• Publisher: American Physical Society (APS)
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY