软玻璃超低速弹道动力学的直接空间研究
Direct-space investigation of the ultraslow ballistic dynamics of a soft glass
摘要：
我们使用光学显微镜来研究由紧密堆积的软球制成的玻璃的老化动力学，从流体到固体状状态的快速转变。通过测量时间分辨的，粗粒度的位移场，我们确定了两类动力学事件，分别对应于可逆和不可逆的重排。可逆事件是由于施加于样品的小的、实验上不可避免的温度波动，导致引起剪切变形的瞬时热膨胀和收缩。不可逆事件是塑性重排，诱导的反复剪切循环。我们表明，由于不可逆重排的位移随时间线性增长，在平均水平和在本地水平。与这种弹道运动相关的速度随样品年龄呈指数下降，解释了观察到的动力学减慢。由于不可逆重排的位移场具有涡旋状结构，并且在令人惊讶的长距离上空间相关。
英文摘要：
We use light microscopy to investigate the aging dynamics of a glass made of closely packed soft spheres, following a rapid transition from a fluid to a solid-like state. By measuring time-resolved, coarse-grained displacements fields, we identify two classes of dynamical events, corresponding to reversible and irreversible rearrangements, respectively. The reversible events are due to the small, experimentally unavoidable fluctuations of the temperature imposed to the sample, leading to transient thermal expansions and contractions that cause shear deformations. The irreversible events are plastic rearrangements, induced by the repeated shear cycles. We show that the displacement due to the irreversible rearrangements grows linearly with time, both on average and at a local level. The velocity associated with this ballistic motion decreases exponentially with sample age, accounting for the observed slowing down of the dynamics. The displacement field due to the irreversible rearrangements has a vortex-like structure and is spatially correlated over surprisingly long distances.
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