期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2020
卷号：117
期号：11
页码：5714-5718
DOI：10.1073/pnas.1917283117
出版社：The National Academy of Sciences of the United States of America
摘要：The replica theory of glasses predicts that in the infinite dimensional mean field limit, there exist two distinct glassy phases of matter: stable glass and marginal glass. We have developed a technique to experimentally probe these phases of matter using a colloidal glass. We avoid the difficulties inherent in measuring the long time behavior of glasses by instead focusing on the very short time dynamics of the ballistic to caged transition. We track a single tracer particle within a slowly densifying glass and measure the resulting mean squared displacement (MSD). By analyzing the MSD, we find that upon densification, our colloidal system moves through several states of matter. At lowest densities, it is a subdiffusive liquid. Next, it behaves as a stable glass, marked by the appearance of a plateau in the MSD whose magnitude shrinks with increasing density. However, this shrinking plateau does not shrink to zero; instead, at higher densities, the system behaves as a marginal glass, marked by logarithmic growth in the MSD toward that previous plateau value. Finally, at the highest experimental densities, the system returns to the stable glass phase. This provides direct experimental evidence for the existence of a marginal glass in three dimensions.
