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TT: Fachverband Tiefe Temperaturen

TT 90: Quantum Impurities and Kondo Physics

TT 90.4: Vortrag

Donnerstag, 12. März 2026, 17:45–18:00, CHE/0091

Kondo effect competing superconductivity in Van Hove systems — •Grzegorz Michałek and Krzysztof P. Wójcik — Institute of Molecular Physics, Polish Academy of Sciences, ul. M. Smoluchowskiego 17, 60-179 Poznań, Poland

Higher-order Van Hove singularities, characterized by a power-law divergence in the electron density of states near the Fermi surface, are known to boost effects of electronic correlations and in general destabilize conventional Fermi-liquid states. We investigate the influence of such singularity on the magnetic impurity in a superconductor. In general, the Kondo effect is known to compete with superconductivity. Due to this competition, the impurity is expected to undergo a transition between the screened phase, where Kondo screening locally overcomes the superconducting pairing, and Yu-Shiba-Rusinov in-gap state formation, where impurity moment remains intact [1]. We use numerical renormalization group calculations to analyze how a singularity in the normal-state density of states influences the Kondo scale. By incorporating modified density of states into the BCS gap equation, we show the evolution of the Kondo quantum critical point with singularity exponent r.
[1] K. Satori, H. Shiba, O. Sakai, Y. Shimizu, J. Phys. Soc. Jpn. 61, 3239 (1992).

Keywords: Kondo effect; Van Hoove singularities; quantum phase transition; quantum critical point; numerical renormalization group