Rheological Response of a Colloidal Glass with Large Size Bidispersity

Soft glasses, in the form of colloids, emulsions etc., have widespread applications in our day-to-day life. In reality, many of these systems have large size dispersity among constituent particles. It is known that such systems have consequently large separation of relaxation timescales, among the constituents. The rheological response of materials like these have not been much explored. We use large-scale molecular dynamics simulations using a model bidisperse colloidal soft-spheres mixture with large size ratio, to study the response to external shear, across a wide range of densities. The system shows complex macro rheological response, and we try to understand these observations by probing the microscopic structural and dynamical properties of the system. We demonstrate that the interplay of the time scales associated with applied shear and the intrinsic relaxation of the species leads to the observed density-dependent response. Also, by varying the composition of the mixture, we illustrate that increasing the concentration of smaller species leads a softer material, which thus provides a pathway to control the rheology.