Research: Kagome lattice with Kondo effect and unconventional magnetism

Magnetic exchange coupling between conduction electrons and localized f  electrons gives rise to interesting phenomena, such as the Kondo effect, when conduction electrons are scattered by local magnetic moments, resulting in an increase of resistivity in metals at low temperatures; or the emergence of cross-talk between f states localized on different atoms by means of conduction electrons (Ruderman-Kittel-Kasuya-Yosida interaction). If the conduction states inherit topological properties from the crystal structure, it may give rise to an unusual observation.

In the intermetallic compound YbV₆Sn₆, the vanadium atoms form a kagome lattice with typical band features, including the flat band (FB), Dirac point (DP), and van Hove singularities (vHSs), while Yb atoms form a Kondo lattice hosting 4f electrons potent for hybridization. The spectroscopic evidence for the entanglement of these two sublattices was directly visualized by ARPES, as reported by the team of researchers. Further theory calculations confirmed that the interaction occurs between the vanadium kagome states and Yb 4f electrons. In a conventional Kondo system, the Kondo coupling and RKKY interaction compete with each other; in established Yb-based systems, the negative pressure shifts the balance from magnetic ordering to Kondo scattering, as suggested by the Doniach diagram. However, this conventional Kondo paradigm fails to account for the current experimental observations where the underlying antiferromagnetism strengthens under negative pressure, indicating an exotic origin.

This work demonstrates the strong entanglement between the Kondo and kagome sublattices and an unconventional magnetic ground state in YbV₆Sn₆. The interplay between Kondo physics and kagome physics gives rise to the unusual behaviors of kagome-state-mediated exchange interactions. As such, YbV₆Sn₆ is a unique platform to explore unconventional many-body physics beyond the standard Kondo picture.

R. Lou, M. Mende, R. Vocaturo, H. Zhang, Q. Dong, M. Li, P. Ding, E. Cheng, Z. Liao, Y. Zhang, J. Lin, R. Firouzmandi, V. Kocsis, L. T. Corredor, Y. Prots, O. Suvorov, A. Jana, J. Fujii, I. Vobornik, O. Janson, W. Zhu, J. van den Brink, C. Krellner, M. Pan, B. Wang, T. Xia, J. Cheng, S. Wang, C. Felser, B. Büchner, S. Borisenko, R. Yu, D. V. Vyalikh, A. Fedorov,
Strongly Entangled Kondo and Kagome Lattices and the Emergent Magnetic Ground State in Heavy-Fermion Kagome Metal YbV₆⁢Sn₆,
Phys. Rev. Lett. 135, 146902 (2025) (arXiv)