Work

Identification and optimization of accurate spin models for Fermi-Hubbard ladders using matrix product states

Year: 2026

Type: article

Abstract: Open-shell nanographenes offer a controlled setting to study correlated magnetism emerging from π -electron systems. Here, we study non-bipartite Fermi-Hubbard ladders describing oligo(indenoindene) molecules. These feature a gapped, weakly dispersing manifold of quasizero modes in their single-particle spectra, and we show that their low-energy properties can be effectively mapped onto an interacting set of spin-1/2 degrees of freedom. Using density matrix renormalization group simulations of the full Fermi-Hubbard model, we obtain their excitation spectra, entanglement profiles, and spin-spin correlations. We then construct optimized delocalized fermionic modes that act as emergent spins and demonstrate that their interactions are well described by a frustrated J 1 – J 2 Heisenberg chain. This effective description clarifies how spin degrees of freedom arise and interact in non-bipartite nanographene ladders, providing a compact and accurate representation of their correlated behavior.

Source: Physical review. B./Physical review. B

DOI: 10.1103/l88j-p4f3

Authors: Andoni Agirre, Thomas Frederiksen, Géza Giedke, Tobias Graß

Institutions: University of the Basque Country, Donostia International Physics Center, Ikerbasque

Language: English

Topic: Quantum many-body systems

Subfield: Atomic and Molecular Physics, and Optics

Field: Physics and Astronomy

Domain: Physical Sciences

Open Access status: hybrid

Funders: European Commission, Eusko Jaurlaritza, Agencia Estatal de Investigación, NextGenerationEU