Dresden 2026 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 62: Correlated Electrons – Poster II
TT 62.10: Poster
Mittwoch, 11. März 2026, 15:00–17:00, P4
Using 1/N graph expansions to explore the mesoscopic regime of strongly correlated systems — •Andreas Schellenberger1, Lidia Stocker2, and Kai Phillip Schmidt1 — 1Friedrich-Alexander-Universität Erlangen-Nürnberg — 2Max Planck Institute for the Physics of Complex Systems, Dresden
Finite-size effects in strongly correlated systems can generate nontrivial low-energy behavior in the mesoscopic regime, yet this regime is difficult to access with standard many-body techniques [1–3]. We present a novel graph-expansion method to systematically explore strongly correlated systems with one-to-all couplings. This approach enables controlled exploration of the corrections to the thermodynamic limit in terms of a 1/N expansion for light-matter systems or systems with collective bath modes.
We apply our approach to the open Kondo box model at zero temperature [4], where an Anderson impurity is coupled to a bath with finite level spacing. By computing energies, correlation functions, and entanglement measures, we investigate how the Kondo effect emerges as a function of the systems parameters, benchmarking our results against exact diagonalization and DMRG.
[1] K. Lenk, J. Li, P. Werner, M. Eckstein, arXiv:2205.05559 (2022)
[2] A. Kudlis, D. Novokreschenov, I. Iorsh, I. Tokatly, arXiv:2304.00805 (2023)
[3] P. Simon, I. Affleck, PRL 89.206602 (2002)
[4] C. Rössler et al., PRL 155.166603 (2015)
Keywords: Kondo box model; Anderson impurity model; 1/N expansion; Full graph expansion; Numerical linked cluster expansion