Shear Flows and Shear Viscosity in a Two-Dimensional Yukawa System (Dusty Plasma)

The shear viscosity of a two-dimensional liquid-state dusty plasma was measured experimentally. A monolayer of highly charged polymer microspheres, with a Yukawa interaction, was suspended in a plasma sheath. Two counterpropagating ${\mathrm{A}\mathrm{r}}^{+}$ laser beams pushed the particles, causing shear-induced melting of the monolayer and a shear flow in a planar Couette configuration. By fitting the particle velocity profiles in the shear flow to a Navier-Stokes model, the kinematic viscosity was calculated; it was of order $1\mathrm{m}{\mathrm{m}}^2{\mathrm{s}}^{-1}$, depending on the monolayer's parameters and shear stress applied.