Spin excitations in nanographene-based antiferromagnetic spin-1/2 Heisenberg chains
Antiferromagnetic Heisenberg chains exhibit two distinct types of excitation spectrum: gapped for integer-spin chains and gapless for half-integer-spin chains. However, in finite-length half-integer-spin chains, quantization induces a gap, requiring precise control over sufficiently long chains to study its evolution. Here we create length-controlled spin-1/2 Heisenberg chains by covalently linking Olympicenes-Olympic-ring-shaped magnetic nanographenes. With large exchange interactions, tunable lengths and negligible magnetic anisotropy, this system is ideal for investigating length-dependent spin excitations, probed via inelastic electron tunnelling spectroscopy. We observe a power-law decay of the lowest excitation energy with length L, following a 1/L dependence in the large-L regime, consistent with theory. For L = 50, a V-shaped excitation continuum confirms a gapless behaviour in the thermodynamic limit. Additionally, low-bias current maps reveal the standing wave of a single spinon in odd-numbered chains. Our findings provide evidence for the realization of a one-dimensional analogue of a gapless spin liquid within an artificial graphene lattice.
Authors
- Lin Yang (ORCID: https://orcid.org/0000-0002-1040-6114)
- Chenxiao Zhao (ORCID: https://orcid.org/0000-0003-4043-4797)
- Ji Ma (ORCID: https://orcid.org/0000-0003-4418-2339)
- Román Fasel (ORCID: https://orcid.org/0000-0002-1553-6487)
- Pascal Ruffieux (ORCID: https://orcid.org/0000-0001-5729-5354)
- J. Fernández‐Rossier (ORCID: https://orcid.org/0000-0003-2297-0289)
- Gonçalo Catarina (ORCID: https://orcid.org/0000-0002-7341-0495)
- Carlo A. Pignedoli (ORCID: https://orcid.org/0000-0002-8273-6390)
- J. C. G. Henriques (ORCID: https://orcid.org/0000-0002-1508-6738)
- Mar Ferri-Cortés (ORCID: https://orcid.org/0009-0007-7910-5516)
- Xinliang Feng (ORCID: https://orcid.org/0000-0003-3885-2703)
Institutions
- University of Bern (CH)
- University of Alicante (ES)
- Universidade de Santiago de Compostela (ES)
- Max Planck Institute of Microstructure Physics (DE)
- International Iberian Nanotechnology Laboratory (PT)
- University of Chinese Academy of Sciences (CN)
- Swiss Federal Laboratories for Materials Science and Technology (CH)
- Technische Universität Dresden (DE)
Publication Details
- Journal
- Nature Materials
- Published
- 2025-03-14
- DOI
- https://doi.org/10.1038/s41563-025-02166-1
- Citations
- 27
- Primary Topic
- Physics of Superconductivity and Magnetism
- Type
- article
- Field-Weighted Citation Impact
- 32.71
Funders
- National Science Foundation
- European Commission
- Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung
- National Natural Science Foundation of China
- Generalitat Valenciana
- Centro Svizzero di Calcolo Scientifico
- National Supercomputing Centre Singapore
- Horizon 2020 Framework Programme
- Fundação para a Ciência e a Tecnologia