From equilibrium to steady state: the transient dynamics of colloidal liquids under shear

We investigate stresses and particle motion during the start-up of flow in a colloidal dispersion close to arrest into a glassy state. A combination of molecular dynamics simulation, mode-coupling theory and confocal microscopy experiments is used to investigate the origins of the widely observed stress overshoot and (previously not reported) super-diffusive motion in the transient dynamics. A link between the macro-rheological stress versus strain curves and the microscopic particle motion is established. Negative correlations in the transient autocorrelation function of the potential stresses are found responsible for both phenomena, and arise even for homogeneous flows and almost Gaussian particle displacements.