Institute of Industrial Science, University of Tokyo

1. Hidden order in supercooled liquids Diverging correlation length and slow dynamics Numerical and experimental evidence for static signature of dynamic heterogeneity in supercooled liquids Institute of Industrial Science, University of Tokyo Hajime Tanaka, Hiroshi Shintani, Takeshi Kawasaki, and Keiji Watanabe Dynamic Heterogeneity and Medium-range Crystalline Order (MRCO) Dynamic heterogeneity is considered to be a clue to the mechanism of the liquid-glass transition, but the physical origin of dynamic heterogeneity has not been clarified. Recent numerical studies and experiments demonstrated the existence of medium-range crystalline order (MRCO) in supercooled liquids, and suggested that MRCO may be the origin of dynamic heterogeneity. 2D spin liquid (2DSL) Driven Granular Matter as a Model System (2DGL) Distribution of Trajectory ガラス板 1.0 0.8 0.6 0.4 0.2 H. Shintani and H. Tanaka, Nat. Phys. 2, 200 (2006). 0.0 2D polydiperse colloidal system (2DPC) Fitting by 2D Ornstein-Zernike function: by T. Kawasaki et al. T. Kawasaki, T. Araki & H. Tanaka, PRL 99, 215701 (2007). K.Watanabe & H. Tanaka, PRL 100,158002 (2008). Absence of static spatial density correlation 2DPC 2DGL There is no indication of static density correlation in S(q) in the region of q ～1/ξ. Instead, there are shoulders in the main peak and splitting of the second peak. The fact that MRCO does not accompany any density change means that MRCO cannot be detected by the two-point density correlator. 3DPC 2DSL 2DSL 2DPC Relationship between MRCO and Dynamic Heterogeneity The Message of our work Contrary to the common belief, we demonstrate that there is ‘static’ heterogeneity in an instantaneous structure of a supercooled liquid, if we look it through the proper order parameter, and it is the origin of ‘dynamic heterogeneity’. However, since medium-range crystalline order (MRCO) does not accompany the density change, MRCO cannot be detected by the static two-body density correlator. We propose that slow dynamics is caused by the critical-like divergence of MRCO toward the ideal glass transition point. This scenario suggests an intriguing link between glass-transition and critical phenomena.