Fifth Order Susceptibility Unveils the Growth of Thermodynamic Amorphous Order in Glass Formers

Orateur : François LADIEU (SPEC, CEA Saclay, Gif-sur-Yvette)

The microscopic mechanisms generating the glass state are still controversially debated : glasses are considered either as merely hyper-viscous liquids or as resulting from a genuine thermodynamic phase transition towards a rigid state. We show that third and fifth order susceptibilities provide a definite answer to this longstanding controversy. We have performed high precision dielectric experiments in two independent setups, yielding consistent results. More precisely, we have measured the third and fifth-order response respectively at the third and fifth harmonics in supercooled glycerol and propylene carbonate. We find strong support for theories based upon thermodynamic amorphous order.

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