Dresden 2026 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 26: Correlated Magnetism – Frustrated Systems
TT 26.1: Talk
Tuesday, March 10, 2026, 09:30–09:45, HSZ/0103
Finite-temperature Lanczos approach to frustrated quantum spin systems — •Andreas Honecker1, Malo Rouxel1, and Katarína Karl’ová2 — 1Laboratoire de Physique Théorique et Modélisation, CNRS, CY Cergy Paris Université, France — 2Department of Theoretical Physics and Astrophysics, P.J. Šafárik University, Košice, Slovakia
The finite-temperature Lanczos method or its quantum typicality variants are a method of choice for computing thermodynamic properties of frustrated quantum spin systems, in particular in two dimensions. Here we show that quasi-exact results can be obtained with moderate numerical effort for systems with N≤40 spins 1/2, even if the method involves Monte Carlo sampling. We illustrate the approach on the diamond-decorated square and honeycomb lattices. These models not only distinguish themselves by the presence of local conservation laws, but also offer a rich phase diagram, including phases with macroscopic ground-state degeneracy. We comment in particular on the resulting enhanced magnetocaloric effect [1].
[1] K. Karľová, A. Honecker, N. Çaçi, S. Wessel, J. Strečka, T. Verkholyak, Phys. Rev. B 110, 214429 (2024).
Keywords: Exact diagonalization; Quantum spin models; Frustrated magnetism