Kawasaki Takeshi, Tanaka Hajime
Institute of Industrial Science, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan.
Phys Rev E Stat Nonlin Soft Matter Phys. 2014 Jun;89(6):062315. doi: 10.1103/PhysRevE.89.062315. Epub 2014 Jun 26.
When a liquid is rapidly quenched to a temperature below the glass-transition point, it is driven out of equilibrium; it then slowly relaxes to a (quasi)equilibrium state. This slow relaxation process is called aging. By definition, any glasses are inevitably in the process of aging and actually slowly evolving with time. Thus the study of aging phenomena is of fundamental importance for understanding not only the nonequilibrium nature of the glass transition, but also the stability of glassy materials. Here we consider aging after a rather shallow quench, for which a system is still able to reach (metastable) equilibrium. By using polydisperse colloidal liquids as a model, we show the validity of dynamical scaling that there is only one relevant length scale not only for a quasiequilibrium supercooled state but also for a nonequilibrium process of aging, which is reminiscent of dynamical critical phenomena. Our finding indicates that the aging toward (metastable) equilibrium may be regarded as the growth process of critical-like fluctuations of static order associated with low-free-energy configurations, further suggesting that this ordering is the origin of cooperative slow dynamics in the systems studied. The generality of this statement for other glass-forming systems remains for a future study.
当一种液体被迅速冷却到玻璃化转变温度以下时，它就会偏离平衡态；然后它会缓慢弛豫到一个（准）平衡态。这种缓慢的弛豫过程被称为老化。根据定义，任何玻璃都不可避免地处于老化过程中，并且实际上会随着时间缓慢演变。因此，老化现象的研究不仅对于理解玻璃化转变的非平衡性质，而且对于理解玻璃态材料的稳定性都具有至关重要的意义。在这里，我们考虑在相当浅的淬火之后的老化情况，对于这种情况，一个系统仍然能够达到（亚稳）平衡。通过使用多分散胶体液体作为模型，我们展示了动态标度的有效性，即不仅对于准平衡过冷态，而且对于老化的非平衡过程，都只有一个相关的长度尺度，这让人联想到动态临界现象。我们的发现表明，向（亚稳）平衡的老化可以被视为与低自由能构型相关的静态序的类临界涨落的增长过程，进一步表明这种有序化是所研究系统中协同慢动力学的起源。这一说法对于其他玻璃形成系统的普遍性仍有待未来研究。
