Soft modes - Parshin, Gurevich

1993 pARSHIN - REVIEW Soft potential model and universal properties of glasses

Vibrational instability, two-level systems, and the boson peak in glasses

D. A. Parshin

In summary, we have shown that the same physical mechanism is fundamental for such seemingly different phenomena as the formation of the two-level systems in glasses and the boson peak in the reduced density of low-frequency
vibrational states. In this way, **two of the most fundamental properties of glasses are interconnected

In our theory, it follows naturally. The physical reason for the small value of the parameter C is that only a small fraction of all created TLS’s can actually tunnel in realistic time scales.

• https://arxiv.org/pdf/0711.0461.pdf

https://arxiv.org/pdf/cond-mat/0203165.pdf