Innsbruck Team Observes Bethe Strings in Ultracold Cesium Gas
Researchers at the University of Innsbruck have experimentally created and observed 'Bethe strings,' a quantum many-body state predicted by Nobel laureate Hans Bethe in 1931. By cooling cesium atoms to near absolute zero and confining them in one-dimensional tubes, the team induced attractive interactions that bound particles into clusters of six or more. These structures, which lack chemical bonds, were verified by their ability to collide without disintegrating. The findings, published in Nature Communications, provide a new, highly controllable platform for studying quantum many-body systems.