Ning Xu (徐宁) Department of Physics, Hefei National Laboratory for Physical Sciences at the Microscale, & CAS Key Laboratory of Soft Matter Chemistry, University of Science and Technology of China

Abstract: A liquid jams into an amorphous solid, e.g. glass, when it is quickly quenched or compressed.  At zero temperature and shear stress, packings of frictionless spheres undergo the jamming transition at a critical-like point J in the framework of the jamming phase diagram.  The criticality of Point J has been extensively studied recently.  The physics of Point J has important implications to some long-standing problems such as the glass transition. 
In this talk, I will present our recent progress in the study of jamming.  At T=0, we discover a crossover volume fraction that separates marginal jamming near Point J from deep jamming at high volume fractions.  Deeply jammed solids show distinct properties in critical scalings, structure, and vibrations from marginally jammed solids, so deep jamming may unveil a new field of amorphous solids that calls for further studies.  In the vicinity of Point J at T>0, the first peak of the pair distribution function exhibits a maximum at a crossover volume fraction (pressure) varying with the temperature.  We find that this crossover is accompanied with changes of material properties.  Surprisingly, multiple quantities show critical scaling collapse, implying the criticality of Point J.
Date & Time: Dec.1, 2011   10:30 – 11:30 a.m.
Location: 606 Conference Room