Spin excitations in nanographene-based antiferromagnetic spin-1/2 Heisenberg chains
Year: 2025
Type: article
Abstract: 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.
Source: Nature Materials
Institutions: Swiss Federal Laboratories for Materials Science and Technology, Max Planck Institute of Microstructure Physics, Center for Advancing Electronics Dresden, Technische Universität Dresden, Universidade de Santiago de Compostela, International Iberian Nanotechnology Laboratory, University of Alicante, University of Chinese Academy of Sciences, University of Bern
Language: English
Subfield: Condensed Matter Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $12,690
Funders: National Science Foundation, Wellcome Trust, 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, H2020 European Research Council
Awards: G1047231290, G120905174, G1530851820, G1724840934, G2512676010, G2574434652, G2636449893, G2666324051, G2919316137, G2950804095, G3291038552, National Research Plan for Lassa Fever in Nigeria, G357246561, G3615212929, Excitações em materiais quânticos 2D, G3783317134, NCCR MARVEL: Materials’ Revolution: Computational Design and Discovery of Novel Materials (phase III), G4872312509, G4937468798, On-surface synthesis of carbon-based quantum spin systems (SYNC), G5098118672, G5175525644, G531036588, Twinning on Functional Layered Materials for Advanced Applications, G5497560422, Bottom-up design and exploration of p-electron quantum magnetism, MULTI-ELECTRON PROCESSES FOR LIGHT DRIVEN ELECTRODES AND ELECTROLYTES IN CONVERSION AND STORAGE OF SOLAR ENERGY, G6633395579, Development of Thiophene Based Conjugated Polymers in Two Dimensions, G7658037602, G8186726090, G8211922251
OpenAlex ID: W4408468122