Dresden 2017 – wissenschaftliches Programm
CPP 37.5: Hauptvortrag
Mittwoch, 22. März 2017, 11:15–11:45, ZEU 255
Nonlinear dielectric spectroscopy in supercooled liquids — Peter Lunkenheimer1, Marion Michl1, Thomas Bauer1, Francois Ladieu2, Samuel Albert2, and •Alois Loidl1 — 1Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, Germany — 2SPEC, CEA, CNRS, University Paris-Saclay, France
We summarize the recent experimental status in non-linear dielectric spectroscopy on supercooled liquids. Nonlinearity can be measured by comparing the complex dielectric constants of high- and low-field permittivities  or by the determination of the higher harmonics of the permittivity . Performing high-precision nonlinear dielectric experiments on glycerol and propylene carbonate, we find experimental evidence for growing cooperativity, implying clusters containing correlated molecules on approaching the glass transition. We were able to demonstrate that the number of dynamically correlated particles increases in much the same way as the effective energy barrier,  as predicted fifty years ago by Adam and Gibbs. By comparing third and fifth order susceptibilities, we again document the increase of amorphous order on decreasing temperatures. Moreover, we were able to determine the fractal dimension of these growing clusters. We find that they are compact and thus the glass transition can be regarded as a critical phenomenon, different from canonical phase transitions .
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 S. Albert et al., Science 352, 1308 (2016).