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arXiv · 2503.14326

Fragility of local moments against hybridization with flat bands

Max Fischer·Arianna Poli·Lorenzo Crippa·Dumitru Călugăru·Sergio Ciuchi·Matthias Vojta·Alessandro Toschi·Giorgio Sangiovanni
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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 consider sharp features in the hybridization function near the Fermi energy. Divergencies of this kind can play a relevant role in twisted bilayer graphene, for which local-moment formation and isospin entropy at finite temperature are currently under the spotlight. We clarify how a low-frequency singularity impacts the screening mechanisms by means of a toy model with a tunable $\delta$-peak in the hybridization function, superimposed to a regular part. Our analysis unveils an unexpectedly big impact on the local-moment physics already for a parametrically small weight of the flat band in the bath.

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Max Fischer, Arianna Poli, Lorenzo Crippa, Dumitru Călugăru, Sergio Ciuchi, Matthias Vojta, Alessandro Toschi, Giorgio Sangiovanni. 2025-03-18. Fragility of local moments against hybridization with flat bands. https://doi.org/10.1103/8x8j-grql

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