Dresden 2006 – wissenschaftliches Programm

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DF: Dielektrische Festkörper

DF 5: Glass I (together with division ‘Dynamics and Statistical Physics’ [DY])

DF 5.1: Hauptvortrag

Dienstag, 28. März 2006, 09:30–10:10, M{\"U}L Elch

Towards a Statistical Mechanics for Network Glasses — •Reimer Kühn¹, Jort M. van Mourik², Martin Weigt³, and Annette Zippelius⁴ — ¹King’s College London, UK — ²Aston University, Birmingham, UK — ³Institute for Scientific Interchange, Torino, Italy — ⁴Universität Göttingen, Germany

We introduce models of heterogeneous systems with finite connectivity defined on random graphs, to capture effects of finite coordination characteristic of finite dimensional systems. Our models use a description in terms of small deviations from a set of reference positions, appropriate for the description of low-temperature phenomena. A Born-von-Karman type expansion with random coefficients is used to model glassy systems. Gel-phases can be described when anharmonicities are absent. The key quantity in the theoretical analysis is a distribution of effective single-site potentials. For gels, where anharmonicities are absent in the interactions, the single-site potentials are harmonic as well, and their distribution is equivalent to the distribution of localization lengths used earlier for the description of such systems. With frustration in the interactions and anharmonicities present, the systems develop glassy phases at low temperature, characterized by an ensemble of single- and double-well potentials, the latter with a broad spectrum of barrier heights and asymmetries. The double well potentials are responsible for the universal glassy low-temperature anomalies, as previously described for fully connected systems