Dresden 2026 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 26: Correlated Magnetism – Frustrated Systems
TT 26.6: Talk
Tuesday, March 10, 2026, 10:45–11:00, HSZ/0103
From Open-Shell Nanographenes to Quantum Spin Chains: Controllable Spins in Carbon Ladders — •Andoni Agirre1,2, Thomas Frederiksen1,3, Géza Giedke1,3, and Tobias Graß1,3 — 1Donostia International Physics Center (DIPC), Manuel Lardizabal Pasealekua 4, 20018 Donostia, Basque Country — 2Department of PMAS: Physics, Chemistry and Technology, University of the Basque Country (UPV/EHU), Manuel Lardizabal Pasealekua 3, 20018 Donostia, Basque Country — 3IKERBASQUE, Basque Foundation for Science, Euskadi Plaza 5, 48009 Bilbao, Basque Country
The low-energy electronic structure of nanographenes with open-shell configurations can be faithfully represented by effective quantum spin models, providing a promising route toward carbon-based quantum simulators. Here we demonstrate this correspondence for an oligo-indenoindene molecule, composed of alternating pentagon-hexagon rings and theoretically mapped to a frustrated Fermi-Hubbard ladder. We show that a spin-1/2 Heisenberg chain consisting of only one spin per pentagon and featuring nearest- and next-nearest-neighbor couplings, quantitatively reproduces the molecular excitation spectrum and entanglement structure obtained from matrix-product-state calculations. By systematically identifying the effective spins with delocalized fermionic modes across the molecular backbone, we achieve near-quantitative agreement in both static and dynamical magnetic properties. Our results establish them as experimentally realizable platforms for exploring frustrated magnetism and correlated spin dynamics in purely carbon-based materials.
Keywords: Nanographenes; Density Matrix Renormalization Group (DMRG); Frustrated Heisenberg model; Fermi Hubbard model; Quasi-1D ladder systems