Yielding of colloidal glasses

We studied yielding in two kinds of colloidal glasses: hard spheres at high concentrations without and with a short-range interparticle attraction induced by adding non-adsorbing polymer. Our oscillatory shear and step strain measurements reveal single and two-step yielding in these two kinds of glasses, respectively. This finding is interpreted in terms of a simple picture: the breaking of local topological constraints (cages) and the breaking of nearest-neighbour bonds.