It is widely known that the low-temperature physical properties, such as the heat capacity and thermal conductivity, of a disordered amorphous solid are markedly different from those of its ordered crystalline counterpart. However, the origin of this discrepancy is not known. One of the universal features of disordered solids is the excess vibrational density of states, known as the ‘boson peak’. Here we study the microscopic origin of the boson peak through numerical investigations of the dynamic structure factor of two-dimensional model glasses over a wide frequency–wavenumber range. We show that the boson peak originates from quasi-localized vibrations of string-like dynamical defects. Furthermore, we reveal that these dynamical defects provide a common structural origin for the three most fundamental dynamic modes of glassy systems: the boson peak, fast β relaxation and slow structural relaxation.

众所周知，无序无定形固体的低温物理性质，例如热容量和导热率，与其有序结晶对应物的物理性质明显不同。然而，这种差异的根源尚不清楚。无序固体的普遍特征之一是状态的过度振动密度，称为“玻色子峰”。在这里，我们通过对宽频率 - 波数范围内的二维模型玻璃的动态结构因子的数值研究来研究玻色子峰的微观起源。我们表明，玻色子峰起源于弦状动力学缺陷的准局部振动。此外，我们揭示了这些动力学缺陷为玻璃系统的三种最基本的动力学模式提供了共同的结构起源：