Researchers have shown that an unusual quantum state known as a “fractional Fermi sea” can be deliberately created, opening the door to a previously unknown phase of matter. The work, published in Physical Review Letters, was carried out by the Nägerl group together with theoretical collaborator Alvise Bastianello of the CNRS and Université Paris-Dauphine. The study provides the theoretical foundation for recent experimental work led by Hans-Christoph Nägerl’s group in the Department of Experimental Physics.
The team focused on ultracold Cesium atoms confined to a single dimension. By repeatedly changing how strongly the atoms interacted, cycling them between strong repulsion and strong attraction, they pushed the system far from its normal equilibrium state. Rather than behaving according to the well-established Tomonaga-Luttinger liquid theory, the atoms entered an entirely new critical phase of matter.
This newly predicted phase arises through a process called quantum engineering, showing that carefully controlled interaction cycles can produce forms of quantum matter that do not occur naturally under ordinary conditions.
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