Exotic critical states as fractional Fermi seas in the one-dimensional Bose gas

TL;DR

This paper demonstrates that a driven one-dimensional Bose gas can host fractional Fermi seas with unique critical properties, extending the understanding of quantum critical phases beyond traditional Tomonaga-Luttinger liquids.

Contribution

It introduces the concept of fractional Fermi seas in an integrable Bose gas driven out of equilibrium, revealing a new critical phase with signatures incompatible with TLL.

Findings

Fractional Fermi seas with reduced occupancy emerge in driven Bose gases.

Correlation functions show criticality beyond TLL behavior.

Predictions are applicable to cold atom experiments.

Abstract

Critical quantum field theories occupy a central position in modern theoretical physics for their inherent universality stemming from long-range correlations. As an example, the Tomonaga-Luttinger liquid (TLL) describes a wealth of one-dimensional quantum systems at low temperatures. Its behavior is deeply rooted in the emergence of an effective Fermi sea, leading to power-law correlations and Friedel oscillations. A promising direction to realize systems exhibiting novel universal behavior beyond TLL is through the generalization of the underlying Fermi sea. In this Letter, we show that fractional Fermi seas with reduced occupancy arise in an integrable Bose gas driven out of equilibrium by cyclic changes in interactions from repulsive to attractive. The correlation functions feature signatures of criticality incompatible with a conventional TLL, suggesting a novel critical phase. Our predictions, based on Generalized Hydrodynamics, are directly relevant to cold atoms.