Stokes-Einstein-like scaling across fluidized and caged transport regimes in a driven complex plasma

The Stokes-Einstein (SE) relation links microscopic fluctuations to macroscopic dissipation. Whether it survives in driven-dissipative, strongly coupled systems far from global equilibrium remains an open question. Using a macroscopic dust vortex in a radio-frequency complex plasma, we isolate thermal velocity fluctuations from the dominant azimuthal flow and resolve the local thermodynamic state across the full radial extent of the structure. The shear-fluidized inner vortex core sustains local thermodynamic equilibrium, evidenced by isotropic Maxwell-Boltzmann distributions (R^{2}>0.95) and near-Fickian transport (α≈0.9). Toward the periphery, Coulomb cages re-form and transport becomes subdiffusive, with α decreasing from near-Fickian values in the core to about 0.70-0.75 in the outer resolved shells, accompanied by enhanced non-Gaussian dynamic heterogeneity. Yet both a normalized SE-like ratio and the full SE product including the independently estimated macroscopic viscosity remain approximately constant over the robust shells, yielding a characteristic SE length comparable to the Coulomb cage size. While the macroscopic transport changes character, the local thermodynamic coupling between fluctuations and dissipation does not. These results reveal that fundamental thermodynamic scaling can globally persist in a strongly coupled system, even as nonequilibrium driving produces a spatial coexistence of fluidlike and caged, glassylike transport regimes, with a characteristic transport scale set by the microscopic confinement.