论文标题
低温下无定形系统中超声衰减的通用性
Universality of Ultrasonic attenuation in amorphous systems at low temperatures
论文作者
论文摘要
在中等范围长度尺度上盛行的分子之间的无重新分散相互作用与其声子在较大尺度下诱导的耦合之间的竞争导致无形系统中纳米级子结构的出现。分子间相互作用的复杂性导致其操作员随机化。基于哈密顿量的随机基质建模及其对外部应变场的线性响应，我们表明超声波衰减系数可以表示为与分子动力学相关的两个关键长度尺度的比率。然后，多种材料的比率恒定值对在低温下实验观察到的超声衰减系数的普遍性提供了理论上的解释。
The competition between unretarded dispersion interactions between molecules prevailing at medium range order length scales and their phonon induced coupling at larger scales leads to appearance of nano-scale sub structures in amorphous systems. The complexity of intermolecular interactions gives rise to randomization of their operators. Based on a random matrix modelling of the Hamiltonian and its linear response to an external strain field, we show that the ultrasonic attenuation coefficient can be expressed as a ratio of two crucial length-scales related to molecular dynamics. A constant value of the ratio for a wide range of materials then provides a theoretical explanation of the experimentally observed universality of the ultrasonic attenuation coefficient at low temperatures.
