Berlin 2018 – wissenschaftliches Programm
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DY: Fachverband Dynamik und Statistische Physik
DY 53: Complex Fluids and Soft Matter (joint session DY/ CPP / BP)
DY 53.8: Vortrag
Mittwoch, 14. März 2018, 17:30–17:45, BH-N 334
The delocalization transition in a colloidal glass — •Markus Gruber1, Gustavo Abade1, Matthias Fuchs1, Antonio Puertas2, Nesrin Senbil3, and Frank Scheffold3 — 1U Konstanz, Germany — 2U Almeria, Spain — 3U Fribourg, Switzerland
Using microscopic probe particles we can study local transport processes and structural dynamics, especially of dense colloidal dispersions. In order to examine nonlinear phenomena such as shear melting, an external force has to be applied. We focus on the microscopic analogon of shear melting for the probe in a glassy host. The force on the probe is increased until it can break out of its cage and delocalize [1]. This phenomenon will be called the delocalization transition.
Our model system is a spherical probe particle subject to a constant external force in a colloidal suspension of hard spheres around the glass transition. The statistical dynamics of the probe particle can be expressed by the self-part of the van-Hove-function for the probe particles. We use a refined mode-coupling theory (MCT) approach for the self-intermediate scattering function for this calculation.
We find that the critical force is strongly connected to the strength of the local cages. Furthermore, the van-Hove-function exhibits an exponential tail in force direction, which increases in weight and correlation length when approaching the critical force. This indicates strong dynamical fluctuations, which will dominate measurements of active microrheology. These results are compared to molecular dynamics computer simulations as well as experiments on an emulsion glass.
[1] Gruber, Abade, Puertas, Fuchs, PRE 94, 042602 (2016)