[2608.14477] Linear response across interaction regimes in two-dimensional ferromagnets Skip to main content Search Submit Donate Log in Search arXiv Press Enter to search · Advanced search Condensed Matter > Statistical Mechanics arXiv:2608.14477 (cond-mat) [Submitted on 14 Aug 2026] Title: Linear response across interaction regimes in two-dimensional ferromagnets Authors: Aaron Müller , Pavel E. Dolgirev , Oleksii Malyshev , Eugene Demler View a PDF of the paper titled Linear response across interaction regimes in two-dimensional ferromagnets, by Aaron M\"uller and 3 other authors View PDF HTML (experimental) Abstract: Recent discoveries of two-dimensional (2D) ferromagnets have stimulated intense interest in understanding and controlling their spin transport properties. A central microscopic feature of these systems is that exchange-driven magnon--magnon interactions are strongly momentum dependent: low-momentum magnons interact weakly, while high-momentum ones can scatter strongly and exhibit collective hydrodynamic behavior. Understanding transport in such systems therefore requires a microscopic description capable of capturing ballistic and hydrodynamic regimes on equal footing. The natural framework is the quantum Boltzmann equation (QBE), whose solution is notoriously difficult because of the multidimensional collision integrals. Here, we develop a method based on an efficient representation of distribution functions as sums of Gaussians, which renders the collision integrals tractable. This approach enables accurate solution of the linearized QBE and computation of momentum- and frequency-resolved linear response in 2D ferromagnets across a broad range of temperatures and magnetic fields. In particular, we resolve a temperature-driven crossover from a ballistic regime dominated by weakly interacting low-momentum magnons to a collective hydrodynamic regime governed by strongly interacting high-momentum modes. Applying this method to monolayer CrCl$_3$, we obtain good agreement with recent nitrogen-vacancy-center dephasing experiments that reported anomalous magnetic noise consistent with magnon sound. More broadly, our work establishes a general framework for computing momentum- and frequency-resolved linear response in interacting 2D quantum systems describable within quantum Boltzmann kinetics. Comments: 19 pages, 6 figures Subjects: Statistical Mechanics (cond-mat.stat-mech) ; Strongly Correlated Electrons (cond-mat.str-el) Cite as: arXiv:2608.14477 [cond-mat.stat-mech] (or arXiv:2608.14477v1 [cond-mat.stat-mech] for this version) https://doi.org/10.48550/arXiv.2608.14477 Focus to learn more arXiv-issued DOI via DataCite Submission history From: Aaron Müller [ view email ] [v1] Fri, 14 Aug 2026 16:54:52 UTC (489 KB) Full-text links: Access Paper: View a PDF of the paper titled Linear response across interaction regimes in two-dimensional ferromagnets, by Aaron M\"uller and 3 other authors View PDF HTML (experimental) TeX Source view license Current browse context: cond-mat.stat-mech < prev | next > new | recent | 2026-08 Change to browse by: cond-mat cond-mat.str-el References & Citations NASA ADS Google Scholar Semantic Scholar export BibTeX citation Loading... BibTeX formatted citation × loading... 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