Mahajan Shivam, Ciamarra Massimo Pica
Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371.
CNRS@CREATE LTD, 1 Create Way, #08-01 CREATE Tower, Singapore 138602.
Phys Rev Lett. 2021 Nov 19;127(21):215504. doi: 10.1103/PhysRevLett.127.215504.
The vibrational density of states D(ω) of solids controls their thermal and transport properties. In crystals, the low-frequency modes are extended phonons distributed in frequency according to Debye's law, D(ω)∝ω^{2}. In amorphous solids, phonons are damped, and at low frequency D(ω) comprises extended modes in excess over Debye's prediction, leading to the so-called boson peak in D(ω)/ω^{2} at ω_{bp}, and quasilocalized ones. Here we show that boson peak and phonon attenuation in the Rayleigh scattering regime are related, as suggested by correlated fluctuating elasticity theory, and that amorphous materials can be described as homogeneous isotropic elastic media punctuated by quasilocalized modes acting as elastic heterogeneities. Our numerical results resolve the conflict between theoretical approaches attributing amorphous solids' vibrational anomalies to elastic disorder and localized defects.
固体的振动态密度D(ω)控制着它们的热性质和输运性质。在晶体中，低频模式是根据德拜定律在频率上分布的扩展声子，D(ω)∝ω²。在非晶态固体中，声子被阻尼，在低频时，D(ω)包含超过德拜预测的扩展模式，导致在ωbp处D(ω)/ω²出现所谓的玻色子峰，以及准局域模式。在这里我们表明，如相关涨落弹性理论所暗示的，瑞利散射 regime中的玻色子峰和声子衰减是相关的，并且非晶材料可以被描述为均匀各向同性弹性介质，由作为弹性不均匀性的准局域模式所间断。我们的数值结果解决了将非晶态固体的振动异常归因于弹性无序和局域缺陷的理论方法之间的冲突。
