Kavli Affiliate: Yi Zhou
| First 5 Authors: Wensi Sun, Yanshuang Chen, Wencheng Ji, Yi Zhou, Hua Tong
| Summary:
Hierarchical dynamics in glass-forming systems span multiple timescales, from
fast vibrations to slow structural rearrangements, appearing in both
supercooled fluids and glassy states. Understanding how these diverse processes
interact across timescales remains a central challenge. Here, by combining
direct particle-level observations with a dynamic eigenmode approach that
decomposes intermediate-timescale responses into distinct modes, we reveal the
microscopic organisation of relaxation dynamics in two-dimensional colloidal
systems. We identify five classes of modes characterizing hierarchical
dynamics: (i) quasi-elastic modes, (ii) slow-reversible string modes
contributing to dynamic heterogeneity, (iii) slow-irreversible string modes
leading to flow, (iv) fast-$beta$ modes with fast-reversible strings, and (v)
random noise modes. The emergence of quasi-elastic modes marks the onset of
glassy dynamics, while reversible string modes dominate dynamic heterogeneity
throughout both supercooled and glassy regimes. Our findings offer a unified
microscopic framework for understanding how distinct relaxation processes
interconnect across timescales, illuminating the mechanisms driving glass
formation.
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