Physicists describe a new quantum state called a fractional Fermi sea

A team led by Hanns-Christoph Nägerl, with theorist Alvise Bastianello, described a "fractional Fermi sea": ultracold cesium atoms in a one-dimensional trap driven far from equilibrium by cycling interactions between strong repulsion and attraction. Published in Physical Review Letters, the work underpins recent experiments by the Innsbruck group.

• Cesium atoms in a 1D system were cycled between strong repulsion and attraction
• The highly excited state keeps hidden order visible in Friedel oscillations
• Correlations deviate from Tomonaga-Luttinger liquid theory predictions
• Authors suggest naming the new quasiparticles "super-Fermions"