Supercooled liquids exhibit spatial heterogeneity in the dynamics of their fluctuating atomic arrangements. The length and time scales of the heterogeneous dynamics are central to the glass transition and influence nucleation and growth of crystals from the liquid. Here, we report direct experimental visualization of the spatially heterogeneous dynamics as a function of temperature in the supercooled liquid state of a Pt-based metallic glass, using electron correlation microscopy with sub-nanometer resolution. An experimental four-point space-time correlation function demonstrates a growing dynamic correlation length, ξ, upon cooling of the liquid toward the glass transition temperature. ξ as a function of the relaxation time τ are in good agreement with Adam-Gibbs theory, inhomogeneous mode-coupling theory and random first-order transition theory of the glass transition. The same experiments demonstrate the existence of a nanometer thickness near-surface layer with order of magnitude shorter relaxation time than inside the bulk.

中文翻译：

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通过电子相关显微镜成像的金属玻璃形成液体的空间异质动力学。

过冷液体在其波动原子排列的动力学中表现出空间异质性。非均相动力学的长度和时间尺度是玻璃化转变的核心，并影响液体中晶体的成核和生长。在这里，我们使用亚纳米分辨率的电子相关显微镜，报告了铂基金属玻璃过冷液态下空间异质动力学随温度变化的直接实验可视化。实验四点时空相关函数表明，当液体冷却至玻璃化转变温度时，动态相关长度 xi 不断增长。ψ 作为弛豫时间 τ 的函数与 Adam-Gibbs 理论、非齐次模耦合理论和玻璃化转变的随机一级转变理论非常一致。相同的实验证明存在纳米厚度的近表面层，其弛豫时间比内部层短几个数量级。