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Arthur T Knackerbracket has found the following story:

90 years ago, the physicist Hans Bethe postulated that unusual patterns, so-called Bethe strings, appear in certain magnetic solids. Now an international team has succeeded in experimentally detecting such Bethe strings for the first time. They used neutron scattering experiments at various neutron facilities including the unique high-field magnet of BER II* at HZB. The experimental data are in excellent agreement with the theoretical prediction of Bethe and prove once again the power of quantum physics.

The regular arrangement of atoms in a crystal allows complex interactions that can lead to new states of matter. Some crystals have magnetic interactions in only one dimension, i.e. are they magnetically one-dimensional. If, in addition, successive magnetic moments are pointing in opposite directions , then we are dealing with a one-dimensional antiferromagnet. Hans Bethe first described this system theoretically in 1931, predicting also the presence of excitations of strings of two or more consecutive moments pointing in one direction, so called Bethe strings.

-- submitted from IRC

Journal Reference
Anup Kumar Bera, Jianda Wu, Wang Yang et al. Dispersions of many-body Bethe strings, Nature Physics (DOI: doi:10.1038/s41567-020-0835-7)

Original Submission