Strongly entangled Quantum Spin Rings driven by H\"uckel rule
Abstract
Quantum spin rings represent an intriguing platform for studying unconventional magnetic order and exotic quantum phases, and they are also promising materials for emerging quantum technologies. Conventional spin systems consist of a set of weakly interacting localized spins that are well described by the Heisenberg spin models. Here, we demonstrate that strong interactions between radical centers in macrocycles of different sizes lead to fluctuations in the total number of unpaired electrons and to non-trivial antiferromagnetic order that extends beyond the Heisenberg picture. We demonstrate that the electronic structure of these spin rings is governed by the concept of 4n/4n+2 H\"uckel (anti)aromaticity for even-membered rings, whereas odd-membered rings possess a highly degenerate frustrated magnetic ground state. The strongly coupled spin rings are experimentally realized through the on-surface synthesis of {\pi}-magnetic carbon-based macrocycles, which consist of [2]triangulene units. The close correlation between the electronic structure and the H\"uckel aromaticity rule is revealed by scanning tunneling spectroscopy and multireference calculations. This work establishes a novel design principle employing the concept of H\"uckel aromaticity for quantum spin macrocycles.
Cite
@article{arxiv.2603.17854,
title = {Strongly entangled Quantum Spin Rings driven by H\"uckel rule},
author = {Manish Kumar and Deng-Yuan Li and Zhangyu Yuan and Ying Wang and Diego Soler-Polo and Enzo Monino and Libor Veis and Yi-Jun Wang and Xin-Yu Zhang and Can Li and Jinfeng Jia and Pei-Nian Liu and Pavel Jelinek and Shiyong Wang},
journal= {arXiv preprint arXiv:2603.17854},
year = {2026}
}