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TT: Fachverband Tiefe Temperaturen

TT 62: Correlated Electrons – Poster II

TT 62.8: Poster

Wednesday, March 11, 2026, 15:00–17:00, P4

Electron-phonon coupling for impurity models with flat bands in the bath — •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 Anderson impurity models the hybridization is typically assumed to be constant close to the Fermi level. Extensions including local vibrations coupled to the impurity site have been extensively studied. In this respect, the impact of Holstein phonons on the Kondo effect is particularly interesting, due to the subtle interplay between the exchange coupling and the phonon dynamics. Retardation effects can become particularly relevant since in addition to the bare phonon frequency and the bare kinetic energy, the correlation-induced renormalized bandwidth enters into the game. We add yet another knob, which is the flatness of the fermionic bath and study with analytical, quantum Monte Carlo and renormalization group approaches the effect of a singularity in the hybridization function, following our previous study without phonons [1].

[1] M. Fischer, A.Poli, L. Crippa, D. Călugăru, S. Ciuchi, M. Vojta, A. Toschi, and G. Sangiovanni, arXiv:2503.14326 (2025).

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