Charge fluctuations in the intermediate-valence ground state of SmCoIn5

David W Tam; Nicola Colonna; Neeraj Kumar; Cinthia Piamonteze; Fatima Alarab; Vladimir N Strocov; Antonio Cervellino; Tom Fennell; Dariusz Jakub Gawryluk; Ekaterina Pomjakushina; Y Soh; Michel Kenzelmann

doi:10.1038/s42005-023-01339-1

Charge fluctuations in the intermediate-valence ground state of SmCoIn₅

Commun Phys. 2023;6(1):223. doi: 10.1038/s42005-023-01339-1. Epub 2023 Aug 22.

Authors

Affiliations

¹ Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institut, 5232 Villigen, Switzerland.
² National Centre for Computational Design and Discovery of Novel Materials (MARVEL), Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland.
³ Paul Scherrer Institut, 5232 Villigen, Switzerland.
⁴ Photon Science Division, Paul Scherrer Institut, 5232 Villigen, Switzerland.
⁵ Laboratory for Multiscale Materials Experiments, Paul Scherrer Institute, 5232 Villigen, Switzerland.

Abstract

The microscopic mechanism of heavy band formation, relevant for unconventional superconductivity in CeCoIn₅ and other Ce-based heavy fermion materials, depends strongly on the efficiency with which f electrons are delocalized from the rare earth sites and participate in a Kondo lattice. Replacing Ce³⁺ (4f¹, J = 5/2) with Sm³⁺ (4f⁵, J = 5/2), we show that a combination of the crystal electric field and on-site Coulomb repulsion causes SmCoIn₅ to exhibit a Γ₇ ground state similar to CeCoIn₅ with multiple f electrons. We show that with this single-ion ground state, SmCoIn₅ exhibits a temperature-induced valence crossover consistent with a Kondo scenario, leading to increased delocalization of f holes below a temperature scale set by the crystal field, T_v ≈ 60 K. Our result provides evidence that in the case of many f electrons, the crystal field remains the dominant tuning knob in controlling the efficiency of delocalization near a heavy fermion quantum critical point, and additionally clarifies that charge fluctuations play a general role in the ground state of "115" materials.

Keywords: Electronic properties and materials; Magnetic properties and materials; Phase transitions and critical phenomena; Superconducting properties and materials.