Year: 2026
Type: article
Abstract: Large-spin two-dimensional magnets are generally expected to develop conventional long-range order once the dominant exchange scale becomes appreciable. The layered spin-3/2maple-leaf compound Na2Mn3O7defies this expectation: despite sizable antiferromagnetic interactions and no evident disorder, it exhibits no magnetic ordering and displays two well-separated thermodynamic crossover scales. We show that this behavior originates from a crystallography-driven molecularization of the magnetic degrees of freedom. The low-symmetry structure partitions the Mn sublattice into inequivalent exchange pathways, generating a pronounced hierarchy that nearly isolates antiferromagnetic hexagons. Magnetic correlations therefore develop in two stages: first within individual hexagons at a scale set by the dominant exchange, and only at much lower temperatures do frustrated inter-hexagon couplings attempt to establish coherence across the lattice. While isolated hexagons reproduce the two-step thermodynamic structure, the experimentally relevant temperature scales emerge only once the hexagons are embedded in the frustrated two-dimensional network. The resulting quantum ground state is magnetically disordered, characterized by strong intra-hexagon correlations and rapidly decaying inter-hexagon correlations. These results identify crystallographic inequivalence as a materials-level mechanism for stabilizing molecularized and quantum-disordered states even in large-spin two-dimensional magnets.
Source: Reports on Progress in Physics
Language: English
Subfield: Condensed Matter Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Funders: National Science Foundation, Simons Foundation, Aspen Center for Physics, International Centre for Theoretical Sciences, Deutsche Forschungsgemeinschaft, Abdus Salam International Centre for Theoretical Physics, Indian Institute of Technology Madras, University of Tokyo, Japan Society for the Promotion of Science
Awards: G1352909968, G1533769778, G1750626284, G2152757567, G2158694287, G2492005311, SFB 1170: Topologische und korrelierte Elektronik in Ober und Grenzflächen ("ToCoTronics"), Identification of technologically relevant altermagnets, G3764568615, EXC 2147: Komplexität und Topologie in Quantenmaterialien (CT.QMAT), Kavli Institute for Theoretical Physics, G7076001471, FOR 5249: Quantitative räumlichzeitliche Modellierung von Materie mit elektronischen Korrelationen
OpenAlex ID: W7162497043