复制耦合玻璃形成液体中增长的长度尺度
On the growing length scale in a replica-coupled glassforming liquid
AI总结：
本研究通过计算机模拟揭示复制耦合玻璃形成液体中，随温度降低而迅速增长的长度尺度导致重叠分布出现双峰，但并非一级相变，而是有限尺寸效应，对理解玻璃转变具有重要意义。
摘要：
我们使用计算机模拟研究了一个三维多分散模型玻璃形成体，该模型处于复制耦合设置中，其中强度为$\varepsilon$的吸引力场$\propto - \varepsilon Q$可以通过重叠参数$Q$调整系统与固定参考构型的相似性。模型中的多分散性使得我们能够高效地结合交换蒙特卡洛方法与分子动力学模拟，从而在极低温度下（即远低于模式耦合理论临界温度$T_{\rm MCT}$）获得完全平衡的液体构型。当$\varepsilon$场被激活时，带有交换的快速动力学允许系统在低于$T_{\rm MCT}$的温度下弛豫到稳态。在稳态下，重叠$Q$具有有限值，且该值随$\varepsilon$增大而增大。对于给定温度$T$，重叠围绕平均值的涨落在临界场强$\varepsilon^\star(T)$处达到最大。随着温度沿此$\varepsilon^\star(T)$线降低，重叠涨落增加，并发生从单峰重叠分布到双峰形状的转变。我们提供的证据表明，这些双峰分布并非源于一级相变，而是反映了由于随温度降低而迅速增长的长度尺度所导致的有限尺寸效应。我们讨论了这一长度尺度对理解玻璃转变的重要意义。
英文摘要：
Computer simulations are used to study a three-dimensional polydisperse model glassformer in a replica-coupling setup where an attractive field $\propto - \varepsilon Q$ of strength $\varepsilon$ can adjust the similarity of the system to a fixed reference configuration with the overlap parameter $Q$. The polydispersity in the model enables the efficient use of swap Monte Carlo in combination with molecular-dynamics simulation from which we obtain fully equilibrated liquid configurations at very low temperature, i.e., far below the critical temperature of mode-coupling theory, $T_{\rm MCT}$. When the $\varepsilon$-field is switched on, the fast dynamics with swaps allow relaxation to the stationary state at temperatures below $T_{\rm MCT}$. In the stationary state, the overlap $Q$ has a finite value that increases with increasing $\varepsilon$. For a given temperature $T$, fluctuations of the overlap around the average value become maximal at a critical field strength $\varepsilon^\star(T)$. With decreasing $T$ along this $\varepsilon^\star(T)$-line, overlap fluctuations increase and a transition from a unimodal overlap distribution to a bimodal shape occurs. We give evidence that these bimodal distributions are not due to first-order phase transitions. However, they reflect finite-size effects due to a rapidly growing length scale with decreasing temperature. We discuss the significance of this length scale for the understanding of the glass transition.
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