AI 中文总结
该研究发现过冷液体β弛豫区的动力学关联长度随温度非单调变化，用随机β弛豫理论定量描述，为模式耦合转变的被避免转变图像提供了直接空间证据。
AI 中文摘要
过冷液体中结构弛豫的显著减慢伴随着动力学异质性的出现，在α时间尺度下测得的动力学关联长度单调增长是该现象的显著特征之一。本文表明该图像并不完整：在β弛豫区测得的动力学关联长度呈现出显著的非单调温度依赖关系，在模式耦合转变温度Tc附近达到最大值，进一步降温时会减小，即便局部动力学涨落仍在持续增强。该行为表明，系统从Tc附近空间延展、最大程度协同的运动，转变为Tc以下愈发紧凑且局域化的弛豫事件。我们证明，这种演化可由随机β弛豫理论定量描述，该理论是模式耦合理论超出平均场的扩展，明确预测了有限维度下存在一个被避免的动力学转变。我们的结果为模式耦合转变的被避免转变图像提供了首个直接空间证据，并确立了β区关联长度的峰值作为模式耦合转变的可靠指标。
英文摘要
The dramatic slowing down of structural relaxation in supercooled liquids is accompanied by the emergence of dynamic heterogeneity. A monotonically increasing dynamical correlation length, measured at the $α$-timescale, is one of the remarkable features of this phenomenon. Here we show that this picture is incomplete: the dynamical correlation length measured in the $β$-relaxation regime exhibits a striking non-monotonic temperature dependence, reaching a maximum near the mode-coupling crossover temperature $T_c$ and decreasing upon further cooling, even as local dynamical fluctuations continue to intensify. This behavior suggests a crossover from spatially extended, maximally cooperative motion near $T_c$ to increasingly compact and localized relaxation events below it. We demonstrate that this evolution is quantitatively captured by stochastic beta-relaxation theory, an extension of mode-coupling theory beyond mean-field that explicitly predicts an avoided dynamical transition in finite dimensions. Our results provide the first direct spatial evidence in favor of the avoided-transition picture of the mode-coupling crossover, and establish the peak of the $β$-regime correlation length as a robust indicator of the mode-coupling crossover.
Comments10 pages, 6 figures
