Questioning the relationship between the χ4 susceptibility and the dynamical correlation length in a glass former

Abstract : Clusters of fast and slow correlated particles, identified as dynamical heterogeneities (DHs), con- stitute a central aspect of glassy dynamics. A key ingredient of the glass transition scenario is a significant increase of the cluster size ξ4 as the transition is approached. In need of easy-to-compute tools to measure ξ4 , the dynamical susceptibility χ4 was introduced recently, and used in various ex- perimental works to probe DHs. Here, we investigate DHs in dense microgel suspensions using image correlation analysis, and compute both χ4 and the four-point correlation function G4 . The spatial decrease of G4 provides a direct access to ξ4 , which is found to grow significantly with increasing volume fraction. However, this increase is not captured by χ4 . We show that the assumptions that validate the connection between χ4 and ξ4 are not fulfilled in our experiments.
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Submitted on : Thursday, September 10, 2015 - 9:20:05 AM
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  • HAL Id : hal-01098350, version 3
  • ARXIV : 1412.8130

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Rémy Colin, Ahmed Alsayed, Cyprien Gay, Bérengère Abou. Questioning the relationship between the χ4 susceptibility and the dynamical correlation length in a glass former. 2015. ⟨hal-01098350v3⟩

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