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MON: Monday Contributed Sessions

MON 23: Poster Session: Fundamental Aspects and Model Systems

MON 23.32: Poster

Monday, September 8, 2025, 18:30–20:30, ZHG Foyer 1. OG

Kondo effect with singular baths: the role of electron-phonon interaction — •Max Fischer¹, Emin Moghadas², Niklas Witt¹, Alessandro Toschi², and Giorgio Sangiovanni¹ — ¹Institut für Theoretische Physik und Astrophysik and Würzburg-Dresden Cluster of Excellence ct.qmat, Universität Würzburg, 97074 Würzburg, Germany — ²Institute of Solid State Physics, TU Wien, 1040 Vienna, Austria

In the context of dynamical mean-field theories, the hybridization function of the associated impurity model becomes singular at the Fermi level whenever the density of states vanishes at the Fermi level. One examples is the prominent twisted bilayer graphene where the flat bands form a 2D Dirac cone yielding a peak in the bath of the corresponding periodic Anderson model. This is at odds with standard examples of Kondo systems in which the hybridizations are assumed to be regular and well-behaved around the Fermi energy. By means of quantum Monte Carlo and renormalization group we study the crossover from Kondo to the local-moment regime solving an Anderson impurity model which combines a regular part with a tunable peak at the Fermi level. Furthermore, we couple the impurity electrons to a local Holstein-like degree of freedom and analyze the effect of the oscillator on the Kondo feature. We also investigate in which way the singularity in the bath influences the effects of retardation.

Keywords: Anderson impurity model; Holstein phonons; Kondo physics; Local moments; Renormalization group