Ultracold Atoms Reveal a Fractional Fermi Sea, a New Quantum Phase
Physicists used ultracold cesium atoms confined to one dimension and cyclically shifted their interactions between strong repulsion and attraction, driving the system into a highly excited but highly ordered state called a fractional Fermi sea. This phase exhibits correlations and Friedel oscillations that defy the standard Tomonaga-Luttinger liquid description, pointing to a new critical phase of matter and expanding quantum-simulation possibilities.