Fragility of local moments against hybridization with flat bands

ORAL

Abstract

The Kondo screening of a localized magnetic moment crucially depends on the spectral properties of the electronic bath to which it is coupled. Unlike textbook examples, realistic systems as well as dynamical mean-field theory of correlated lattice models force us to explicitly consider sharp features in the hybridization function near the Fermi energy. A case currently under the spotlight is twisted bilayer graphene, where the hybridization function of the heavy-fermion-like bands to the itinerant ones displays a divergence. We clarify how this impacts the screening mechanisms by means of a toy model with a tunable δ-peak in the hybridization function, superimposed to a regular part. Our analysis [1] unveils an unexpectedly big impact on the Kondo screening already for a parametrically small weight of the flat band in the bath.

[1] https://doi.org/10.48550/arXiv.2503.14326

*M. F. acknowledges financial support by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany's Excellence Strategy through the Würzburg-Dresden Cluster of Excellence on Complexity and Topology in Quantum Matter-ct.qmat (EXC 2147, project-id 390858490) and M. V. through SFB 1143 (project-id 247310070). S. C. acknowledges funding from NextGenerationEU National Innovation Ecosystem grant ECS00000041 - VITALITY - CUP E13C22001060006 and grant PE00000023 - IEXSMA - CUP E63C22002180006. A. T. and G. S. acknowledge financial support through project I 5487 (doi: 10.55776/I5487) by the Austrian Science Fund (FWF) and project Nr. 468199700 by the DFG as well as project I 5868 (doi: 10.55776/I5868), respectively project part P1 and P5 of the FOR 5249 [QUAST] by the DFG Nr. 449872909. D.C. gratefully acknowledges the support provided by the Leverhulme Trust, as well as additional support from the UKRI Horizon Europe Guarantee Grant No. EP/Z002419/1 (for an ERC Consolidator Grant to Siddharth A. Parameswaran).

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Publication: https://doi.org/10.48550/arXiv.2503.14326

Presenters

  • Giorgio Sangiovanni

    • Julius-Maximilians University of Wuerzburg

Authors

  • Giorgio Sangiovanni

    • Julius-Maximilians University of Wuerzburg

  • Max Fischer

    • University of Würzburg

  • Arianna Poli

    • University of l'Aquila

  • Lorenzo Crippa

    • Julius-Maximilians University of Wuerzburg
    • University of Hamburg

  • Dumitru Calugaru

    • University of Oxford

  • Sergio Ciuchi

    • University of l'Aquila
    • University of L'Aquila
    • Università de l'Aquila

  • Matthias Vojta

    • TU Dresden

  • Alessandro Toschi

    • TU Wien
    • Technical University of Vienna