Universal Origin of Boson Peak Vibrational Anomalies in Ordered Crystals and in Amorphous Materials
Universal Origin of Boson Peak Vibrational Anomalies in Ordered Crystals and in Amorphous Materials
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DOI：
10.1103/physrevlett.122.145501
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发表时间：
2019-04-10
影响因子：
8.6
通讯作者：
Zaccone, Alessio
中科院分区：
文献类型：
--
作者：
Baggioli, Matteo;Zaccone, Alessio
在低能状态下，有序和非晶态固体的振动谱控制着材料的热容量、热传导、电子-声子耦合、常规超导性等热学和输运性质。旧的低能量振动谱德拜模型给出了与频率平方成正比的状态振动密度（VDOS），但在许多材料中，谱偏离了这一定律，导致VDOS按频率平方归一化后出现峰值，即所谓的“玻色子峰值”。从第一性原理出发，对固体（晶体和玻璃）的VDOS进行了描述。在不使用任何材料无序性假设的情况下，证明了有序晶体和玻璃的VDOS中的玻色子峰是由弹性模传播和扩散阻尼之间的竞争自然产生的。这一理论解释了最近实验观测到的完全有序晶体中玻色子峰，这是以前的理论框架无法解释的。该理论还首次解释了振动谱如何随着固体原子密度的变化而变化，并解释了最近对这种效应的实验观察。
The vibrational spectra of solids, both ordered and amorphous, in the low-energy regime, control the thermal and transport properties of materials, from heat capacity to heat conduction, electron-phonon couplings, conventional superconductivity, etc. The old Debye model of vibrational spectra at low energy gives the vibrational density of states (VDOS) as proportional to the frequency squared, but in many materials the spectrum departs from this law which results in a peak upon normalizing the VDOS by frequency squared, which is known as the "boson peak." A description of the VDOS of solids (both crystals and glasses) is presented starting from first principles. Without using any assumptions whatsoever of disorder in the material, it is shown that the boson peak in the VDOS of both ordered crystals and glasses arises naturally from the competition between elastic mode propagation and diffusive damping. The theory explains the recent experimental observations of boson peak in perfectly ordered crystals, which cannot be explained based on previous theoretical frameworks. The theory also explains, for the first time, how the vibrational spectrum changes with the atomic density of the solid, and explains recent experimental observations of this effect.