What happens when atoms are repeatedly pushed between different interaction conditions? Researchers have found a way to theoretically create an unusual, ordered state of quantum matter.
Researchers at the University of Innsbruck in Austria, working with theorist Alvise Bastianello of France’s CNRS and Université Paris-Dauphine, have developed a theoretical framework for creating an unusual quantum state known as a fractional Fermi sea. The work explores how carefully controlled interactions can produce quantum behaviour beyond established theoretical models.
The study focuses on ultracold caesium atoms confined to one dimension. By repeatedly changing the forces governing how the atoms interact, researchers show how a system can move from its lowest-energy state into a highly excited state that retains an organised structure.
Ordinarily, fermions occupy available energy states according to quantum mechanical rules, forming what is known as a Fermi sea. In the proposed fractional Fermi sea, the particles follow a different effective occupancy pattern. Despite being highly excited, the system does not become completely disordered.
The researchers identified distinctive patterns in the mathematical correlations between particles, including Friedel oscillations. These patterns differ from those described by Tomonaga-Luttinger liquid theory, a framework commonly used to explain the behaviour of interacting particles in one-dimensional systems.
The findings could help researchers investigate how quantum states can be created and controlled in laboratory systems. Such fundamental research contributes to the wider understanding needed to develop quantum simulation platforms, which allow scientists to study complex quantum behaviour using controllable physical systems.
“This gives us a controlled way to explore quantum matter beyond the usual equilibrium paradigms,” says Yi Zeng, lead author of the study. The work provides a theoretical foundation for further investigation of fractional Fermi seas.
