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Structural origin of slow dynamics in glass-forming liquids
As a liquid is cooled, its dynamics slow significantly as it approaches the glass
transition point, provided crystallization is avoided. With increased supercooling,
the dynamics of the liquid become progressively more heterogeneous, a
phenomenon known as “dynamic heterogeneity.” Since its discovery, this
hallmark of metastable supercooled liquids has attracted considerable attention
in glass science. Despite extensive research, the precise physical origins of
dynamic heterogeneity remain unresolved and subject to debate. In this talk, we
explore the relationship between dynamic heterogeneity and structural order
using numerical simulations of fragile liquids interacting through isotropic
potentials. Our findings reveal that angular ordering, driven by many-body
interactions, plays a pivotal role in the slowing down of supercooled liquid
dynamics [1,2]. We show that dynamic heterogeneity arises from underlying
angular order, with its spatial extent dictated by static order. Furthermore, we
examine how the growth of static angular order is linked to the slowing dynamics.
In fragile liquids displaying super-Arrhenius behavior, elementary particle
rearrangements propagate sequentially, guided by the order-parameter field from
regions of low to high order [2,3]. This sequential propagation results in an
increase in the activation energy required for particle motion in more ordered
regions. Finally, we address the microscopic origins of dynamic cooperativity in
glass-forming liquids [3], shedding new light on how local structural order
influences collective particle dynamics.
This work was supported in part by Specially Promoted Research (JP20H05619)
from the Japan Society for the Promotion of Science (JSPS).
[1] H. Tanaka, Eur. Phys. J. E 35, 113 (2013) ; H. Tanaka, H. Tong, R. Shi, J.
Russo, Nat. Rev. Phys. 1, 333 (2019).
[2] H. Tong and H. Tanaka, Phys. Rev. X 8, 011041 (2018) ; Nat. Commun. 10,
5596 (2019) ; Phys. Rev. Lett. 124, 225501 (2020).
[3] S. Ishino, Y. C. Hu, and H. Tanaka, Nat. Mater. (in press).