Finding the k-gap: phonon dynamics in liquid lead

We are investigating the phonon theory of thermodynamics in liquids which is still awaiting experimental confirmation. At low temperatures the collective dynamics of liquids have close analogues to solids when the local residence time, t, of an atom exceeds its periods of vibration. This results in a rigid local structure at times shorter than t in liquids that support transverse modes, but only with wave-vectors exceeding kg = 1/(2*c*t), the k-gap. Despite this prediction and the growing interest from the liquid and diffraction communities, there is no experimental evidence for the k-gap. Liquid lead is a strong candidate for the first experimental measurement of the k-gap due to its large predicted kg. The main purpose of this proposal is to find the first experimental evidence for the k-gap and provide long-awaited experimental confirmation for a critical addition to liquid theory.

我们正开展液体热力学声子（phonon）理论的研究，该理论目前仍有待实验验证。在低温条件下，当原子的局域停留时间t超出其振动周期时，液体的集体动力学行为与固体存在高度相似的对应关系。这使得在时间尺度短于t的情况下，液体可形成能够支撑横向振动模式的刚性局域结构，但仅当波矢大于k_g = 1/(2·c·t)时，才会存在k间隙（k-gap）。尽管存在上述理论预测，且液体物理与衍射学界的研究关注度与日俱增，但目前仍未发现k间隙的相关实验证据。液态铅（liquid lead）因理论预测的k_g数值较大，是首个实现k间隙实验测量的极具潜力的候选体系。本研究提案的核心目标是首次获取k间隙的实验证据，并为液体理论中这一关键补充内容提供期盼已久的实验验证。