Shear Melting of a Colloidal Glass

We use confocal microscopy to explore shear melting of colloidal glasses, which occurs at strains of similar to 0.08, coinciding with a strongly non-Gaussian step size distribution. For larger strains, the particle mean square displacement increases linearly with strain and the step size distribution becomes Gaussian. The effective diffusion coefficient varies approximately linearly with shear rate, consistent with a modified Stokes-Einstein relationship in which thermal energy is replaced by shear energy and the length scale is set by the size of cooperatively moving regions consisting of similar to 3 particles.