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TT: Fachverband Tiefe Temperaturen
TT 94: Correlated Magnetism – Low-Dimensional Systems
TT 94.2: Vortrag
Freitag, 13. März 2026, 09:45–10:00, HSZ/0101
Kondo-driven magnetic instability in Van Hove metals with sparse impurities — •Krzysztof Wójcik1, Johann Kroha2,3, and Peter Wahl3,2 — 1Institute of Molecular Physics, Polish Academy of Sciences, 60-179 Poznań, Poland — 2Physikalisches Institut, Universität Bonn, Germany — 3SUPA, School of Physics and Astronomy, University of St Andrews, United Kingdom
We analyze a metal exhibiting a higher-order Van Hove singularity at the Fermi level and hosting sparse randomly distributed magnetic impurities. We show that a sharp resonance in the impurity local spectral density,
characteristic of typical Kondo systems, is absent in the Van Hove-Kondo case. Despite the Kondo singlet ground state, the impurities contribute to total entropy and magnetization by affecting the available excited states, and below a critical temperature for any finite density of impurities these contributions dominate over those of the clean host, leading to hitherto unrecognized instabilities. An especially intriguing instability occurs in the case of a particle-hole asymmetric singularity, such as the one recently observed in Sr3Ru2O7 [1]. In such case, despite complete Kondo screening of the impurities, the host becomes magnetically
unstable due to their presence, which leads to a ferromagnetic ground state.
We comment on relation to the surface magnetism observed in Sr3Ru2O7.
[1] C. A. Marques et al., Sci. Adv. 8, eabo7757 (2022).
Keywords: Kondo effect; Van Hove singularity; numerical renormalization group; magnetic instability