Scientists Observe Bethe Strings in Ultracold Atomic Gas for First Time
Researchers at the University of Innsbruck have experimentally observed "Bethe strings" in an ultracold cesium atomic gas, confirming a quantum theory prediction made by physicist Hans Bethe in 1931.
A research team at the University of Innsbruck has successfully observed "Bethe strings" in an ultracold cesium atomic gas, experimentally validating a quantum theory prediction made by physicist Hans Bethe in 1931. The findings were published in Nature Communications.
Bethe strings are bound states of multiple particles that can only exist in one-dimensional quantum systems. Unlike ordinary molecules formed by chemical bonds, they are held together solely by quantum interactions between particles. They have long been considered a significant prediction within the theory of quantum many-body systems.
While Bethe strings were previously detected in solid-state magnetic systems, this new experiment was conducted in an ultracold gas environment. This setting allows scientists to precisely control the conditions under which these particle clusters form and interact. The study involved theoretical collaborators from the University of Amsterdam and the Technical University of Munich.
To create the necessary one-dimensional conditions, cesium atoms were cooled to fractions of a billionth of a degree above absolute zero and confined to thousands of narrow tubes. When the interactions between atoms were switched from repulsive to attractive, the atoms formed bound clusters instead of collapsing. Subsequent experiments demonstrated the stability of these clusters during collisions, confirming their robust nature.