Lahini Yoav, Gottesman Omer, Amir Ariel, Rubinstein Shmuel M
Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, USA.
Phys Rev Lett. 2017 Feb 24;118(8):085501. doi: 10.1103/PhysRevLett.118.085501. Epub 2017 Feb 21.
We observe nonmonotonic aging and memory effects, two hallmarks of glassy dynamics, in two disordered mechanical systems: crumpled thin sheets and elastic foams. Under fixed compression, both systems exhibit monotonic nonexponential relaxation. However, when after a certain waiting time the compression is partially reduced, both systems exhibit a nonmonotonic response: the normal force first increases over many minutes or even hours until reaching a peak value, and only then is relaxation resumed. The peak time scales linearly with the waiting time, indicating that these systems retain long-lasting memory of previous conditions. Our results and the measured scaling relations are in good agreement with a theoretical model recently used to describe observations of monotonic aging in several glassy systems, suggesting that the nonmonotonic behavior may be generic and that athermal systems can show genuine glassy behavior.
皱缩薄片和弹性泡沫中观察到了非单调老化和记忆效应，这是玻璃态动力学的两个标志。在固定压缩下，这两个系统都表现出单调非指数弛豫。然而，当经过一定的等待时间后部分减小压缩时，这两个系统都表现出非单调响应：法向力首先在许多分钟甚至数小时内增加，直到达到峰值，然后才恢复弛豫。峰值时间与等待时间呈线性比例关系，这表明这些系统保留了对先前状态的持久记忆。我们的结果以及测量的标度关系与最近用于描述几个玻璃态系统中单调老化观测结果的理论模型高度吻合，这表明非单调行为可能是普遍存在的，并且无热系统可以表现出真正的玻璃态行为。
