2017/06/13 by Zhe Wang, Jianda Wu, Wang Yang +13 · 139 citations
Physics and Astronomy · #Advanced Condensed Matter Physics #Antiferromagnetism #Bethe ansatz #Bound state #Ising model #Physics #Physics of Superconductivity and Magnetism #Quantum #Quantum many-body systems #Quantum mechanics #Spin (aerodynamics) #String (physics) #cond-mat.quant-gas #cond-mat.str-el #hep-ex #physics.atom-ph
paper · pdf · doi:10.1038/nature25466
published in Nature 554(7691), 219-223 (Nature Portfolio)
arxiv created 2017/06/13 · openalex publication_date 2018/02/01 · arxiv updated 2018/02/13 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/06
Almost one century ago, string states - complex bound states (Wellenkomplexe) of magnetic excitations - have been predicted to exist in one-dimensional quantum magnets and since then become a subject of intensive theoretical study. However, experimental realization and identification of string states in condensed-matter systems remains an unsolved challenge up to date. Here we use high-resolution terahertz spectroscopy to identify string states in the antiferromagnetic Heisenberg-Ising chain SrCo2V2O8 in strong longitudinal magnetic fields. We observe complex bound states (strings) and fractional magnetic excitations (psinons and antipsinons) in the field-induced critical regime, which are precisely described by the Bethe ansatz. Our study reveals that two-string and three-string states govern the quantum spin dynamics close to the quantum criticality, while the fractional excitations are dominant at low energies, reflecting the antiferromagnetic quantum fluctuations.