  When stressed sufficiently, solid materials yield and deform plastically via
reorganization of microscopic constituents. Indeed, it is possible to alter the
micro-structure of materials by judicious application of stress, an empirical
pro- cess utilized in practice to enhance the mechanical properties of metals.
Un- derstanding the interdependence of plastic flow and microscopic structure
in these non-equilibrium states, however, remains a major challenge. Here, we
ex- perimentally investigate this relationship, between the relaxation dynamics
and microscopic structure of disordered colloidal solids during plastic
deformation. We apply oscillatory shear to solid colloidal monolayers and study
their particle trajectories as a function of shear rate in the plastic regime.
Under these cir- cumstances, the strain rate, the relaxation rate associated
with plastic flow, and the sample microscopic structure oscillate together but
with different phases. Interestingly, the experiments reveal that the
relaxation rate associated with plastic flow at time t is correlated with the
strain rate and sample microscopic structure measured at earlier and later
times, respectively. The relaxation rate, in this non-stationary condition,
exhibits power-law shear-thinning behavior and scales exponentially with sample
excess entropy. Thus, measurement of sample static structure (excess entropy)
provides insight about both strain-rate and constituent rearrangement dynamics
in the sample at earlier times.
