Ultracold cesium atoms reveal Bethe strings predicted nearly a century ago‎

In 1931, physicist Hans Bethe predicted that, in certain one-dimensional quantum systems, particles can bind together to form multi-particle states known as Bethe strings. Unlike ordinary molecules, which are held together by chemical bonds, Bethe strings arise purely from interactions between particles and exist only in one dimension. For decades, Bethe strings remained primarily a theoretical concept.