Observation of a transition between dynamical phases in a quantum degenerate Fermi gas

Author
Abstract
A proposed paradigm for out-of-equilibrium quantum systems is that an analog of quantum phase transitions exists between parameter regimes of qualitatively distinct time-dependent behavior. Here, we present evidence of such a transition between dynamical phases in a cold-atom quantum simulator of the collective Heisenberg model. Our simulator encodes spin in the hyperfine states of ultracold fermionic potassium. Atoms are pinned in a network of single-particle modes, whose spatial extent emulates the long-range interactions of traditional quantum magnets. We find that below a critical interaction strength, magnetization of an initially polarized fermionic gas decays quickly, while above the transition point, the magnetization becomes long-lived because of an energy gap that protects against dephasing by the inhomogeneous axial field. Our quantum simulation reveals a nonequilibrium transition predicted to exist but not yet directly observed in quenched s-wave superconductors.
Year of Publication
2019
Journal
Science Advances
Volume
5
Number of Pages
eaax1568
Date Published
2019-08
URL
https://advances.sciencemag.org/content/5/8/eaax1568.full
DOI
10.1126/sciadv.aax1568
JILA PI
Associated Institutes
Journal Article