Institute of Industrial Science, University of Tokyo Hajime Tanaka , Hiroshi Shintani, Takeshi Kawasaki, and Keiji Watanab e Hidden order in supercooled liquid s 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 m edium-range crystalline order (MRCO) in supercooled liquids, and suggested that MRCO may be the origin of dynamic heterog eneity. Dynamic Heterogeneity and Medium-range Crystalline Order (MRCO) H. Shintani and H. Tanaka, Nat. Phys. 2, 200 (2006). Driven Granular Matter as a Model System (2DGL) by T. Kawasaki et al. Diverging correlation length and slow dynamics Relationship between MRCO and Dynamic Heterogeneity k jk j j i n 6 exp 1 6 ) 0 ( ) ( ) ( 6 6 6 r r g r r r g r g exp ) ( ) ( 2 1 6 Fitting by 2D Ornstein-Zernike function: ガガガガ 1.0 0.6 0.4 0.2 0.0 0.8 dt t t j j 6 6 1 Distribution of Trajecto ry 2D polydiperse colloidal system (2DPC) 2D spin liquid (2DSL) 0 2 4 6 8 10 0 0.1 0.2 0.3 0.4 0.5 r/< d > g 6 ( r)/ g ( r) 77.4% 70.0% 62.6% 2DSL 2DPC 2DGL 3DPC Absence of static spatial density correlation The Message of our work Contrary to the common belief, we demonstrate that there is ‘static’ heterogeneity in an in stantaneous structure of a supercooled liquid, if we look it through the proper order parame ter, and it is the origin of ‘dynamic heterogeneity’. However, since medium-range crystalli ne 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 di vergence of MRCO toward the ideal glass transition point. This scenario suggests an intrigu ing link between glass-transition and critical phenomena. T. Kawasaki, T. Araki & H. Tanaka, PRL 99, 215701 (2007). K.Watanabe & H. Tanaka, PRL 100,158002 (200 8). There is no indication of static de nsity correlation in S(q) in the region o f q ~ 1/ξ. Instead, there are shoulders in the main peak and splitting of the second peak. The fact that MRCO does not accompa ny any density change means that MR CO cannot be detected by the two-po int density correlator. 2DSL 2DPC