Experimental observation of Bethe strings

@article{Wang2018ExperimentalOO,
  title={Experimental observation of Bethe strings},
  author={Zhe Wang and Jianda Wu and Wang Yang and Anup Kumar Bera and Dmytro Kamenskyi and Atm Nazmul Islam and Shenglong Xu and Joseph M. Law and Bella Lake and Congjun Wu and Alois Loidl},
  journal={Nature},
  year={2018},
  volume={554},
  pages={219-223}
}
Almost a century ago, string states—complex bound states of magnetic excitations—were predicted to exist in one-dimensional quantum magnets. However, despite many theoretical studies, the experimental realization and identification of string states in a condensed-matter system have yet to be achieved. Here we use high-resolution terahertz spectroscopy to resolve string states in the antiferromagnetic Heisenberg–Ising chain SrCo2V2O8 in strong longitudinal magnetic fields. In the field-induced… 
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