Microscopic origin of Boson peak in amorphous solids

TL;DR

This paper presents a simplified non-analytic model attributing the Boson peak in amorphous solids to fluctuations in coordination numbers, clarifying its microscopic origin.

Contribution

It identifies coordination number fluctuations as the sole cause of the Boson peak, simplifying previous complex explanations.

Findings

Boson peak originates from coordination number fluctuations.

Spring strength fluctuations mainly cause damping, not the Boson peak.

The model offers a direct explanation for the microscopic origin of the Boson peak.

Abstract

We proposed a non-analytic model to explain the microscopic origin of the anomalous vibrational density of states (DOS), the Boson peak (BP), in amorphous solids based on the scalar dynamical matrix of a network with springs and nodes. We argue that disorder can be classified into two factors: fluctuation of spring strength and fluctuation of coordination numbers (the number of springs connected to a node). The results suggest that BP originates solely from fluctuation of coordination numbers, while the fluctuation of spring strength only contributes to the effect of damping and has very limited effect on low frequency DOS. This work converts complexity into simplicity and provides a direct answer to the puzzle of the microscopic origin of BP in amorphous solids.