Mixed-valence state in the dilute-impurity regime of La-substituted SmB6
Homogeneous mixed-valence (MV) behaviour is one of the most intriguing phenomena of f-electron systems. Despite extensive efforts, a fundamental aspect which remains unsettled is the experimental determination of the limiting cases for which MV emerges. Here we address this question for SmB<sub>6</sub>, a prototypical MV system characterized by two nearly-degenerate Sm<sup>2+</sup> and Sm<sup>3+</sup> configurations. By combining angle-resolved photoemission spectroscopy (ARPES) and x-ray absorption spectroscopy (XAS), we track the evolution of the mean Sm valence, v<sub>Sm</sub>, in the Sm<sub>x</sub>La<sub>1-x</sub>B<sub>6</sub> series. Upon substitution of Sm ions with trivalent La, we observe a linear decrease of valence fluctuations to an almost complete suppression at x = 0.2, with v<sub>Sm</sub> ~ 2; surprisingly, by further reducing x, a re-entrant increase of v<sub>Sm</sub> develops, approaching the value of v<sub>imp</sub> ~ 2.35 in the dilute-impurity limit. Such behaviour departs from a monotonic evolution of v<sub>Sm</sub> across the whole series, as well as from the expectation of its convergence to an integer value for x → 0. Our ARPES and XAS results, complemented by a phenomenological model, demonstrate an unconventional evolution of the MV character in the Sm<sub>x</sub>La<sub>1-x</sub>B<sub>6</sub> series, paving the way to further theoretical and experimental considerations on the concept of MV itself, and its influence on the macroscopic properties of rare-earth compounds in the dilute-to-intermediate impurity regime.
Authors
- Fabio Boschini (ORCID: https://orcid.org/0000-0003-3503-9389)
- Davide Curcio (ORCID: https://orcid.org/0000-0003-2488-3840)
- Marco Bianchi (ORCID: https://orcid.org/0000-0002-0122-9443)
- Marta Zonno (ORCID: https://orcid.org/0000-0003-0668-5146)
- Philip Hofmann (ORCID: https://orcid.org/0000-0002-7367-5821)
- Matteo Michiardi (ORCID: https://orcid.org/0000-0001-9640-5093)
- Robert J. Green (ORCID: https://orcid.org/0000-0003-1849-1576)
- I. S. Elfimov
- G. Levy (ORCID: https://orcid.org/0000-0003-2980-0805)
- P. F. S. Rosa (ORCID: https://orcid.org/0000-0002-3437-548X)
- Z. Fisk (ORCID: https://orcid.org/0000-0001-6423-754X)
- G. A. Sawatzky (ORCID: https://orcid.org/0000-0003-1265-2770)
- A. Damascelli (ORCID: https://orcid.org/0000-0001-9895-2226)
- Klara Volckaert (ORCID: https://orcid.org/0000-0002-7353-3540)
Institutions
- Los Alamos National Laboratory (US)
- University of British Columbia (CA)
- University of California, Irvine (US)
- Aarhus University (DK)
- Synchrotron soleil (FR)
- University of Saskatchewan (CA)
- Institut National de la Recherche Scientifique (CA)
- Max Planck Institute for Chemical Physics of Solids (DE)
- Canadian Light Source (Canada) (CA)
Publication Details
- Journal
- Nature Communications
- Published
- 2024-09-02
- DOI
- https://doi.org/10.1038/s41467-024-51569-2
- Citations
- 1
- Primary Topic
- Rare-earth and actinide compounds
- Type
- article
- Field-Weighted Citation Impact
- 0.31
Funders
- U.S. Department of Energy
- Canadian Institute for Advanced Research
- Villum Fonden
- Canadian Light Source
- Canada Research Chairs
- Killam Trusts
- University of Tokyo
- Canada First Research Excellence Fund
- Ministère de la Défense Nationale
- Canadian Institutes of Health Research
- Natural Sciences and Engineering Research Council of Canada
- British Columbia Knowledge Development Fund
- Basic Energy Sciences