Molecular dynamics simulations are performed to investigate heterogeneous
dynamics in amorphous glassy materials under oscillatory shear strain. We
consider three-dimensional binary Lennard-Jones mixture well below the glass
transition temperature. The structural relaxation and dynamical heterogeneity
are quantified by means of the self-overlap order parameter and the dynamic
susceptibility. We found that at sufficiently small strain amplitudes, the mean
square displacement exhibits a broad sub-diffusive plateau and the system
undergoes nearly reversible deformation over about 104 cycles. Upon
increasing strain amplitude, the transition to the diffusive regime occurs at
shorter time intervals and the relaxation process involves intermittent bursts
of large particle displacements. The detailed analysis of particle hopping
dynamics and the dynamic susceptibility indicates that mobile particles
aggregate into clusters whose sizes increase at larger strain amplitudes.
Finally, the correlation between particle mobilities in consecutive time
intervals demonstrates that dynamic facilitation becomes increasingly
pronounced at larger strain amplitudes.Comment: 20 pages, 7 figure