Experimentally accessible drive-induced attractor in a Fermi gas near unitarity

Abstract

Hydrodynamic attractors describe loss of sensitivity to initial conditions. Their earliest, expansion-driven stage is distinct from the later relaxation-driven mechanism and central to the theoretical paradigm but hard to access in heavy-ion collision experiments. We show within a coupled energy-bulk-pressure model that a near-unitary Fermi gas driven by a rapid scattering-length sweep loses sensitivity to one state-space direction before bulk relaxation sets in -- visible only in the joint state space, not as a universal single-variable curve. We outline an experimental ${}^{40}$K protocol based on time-resolved contact measurements and a varied-ramp comparison.

Comments: 8 pages, 3 figures. v2: Corrected formula for energy density, adapted to theoretical model data for contact and bulk viscosity to extend validity to lower temperatures. Several minor changes v3: Major revision of the presentation and framing. Added experimental protocol to End Matter and Fig.4 and discussion to Supplemental Material