Universal non-mean-field scaling in the density of state of amorphous solids

TL;DR

This paper develops a theoretical framework extending mean-field theory to finite dimensions, explaining the universal quartic scaling of excess soft modes in amorphous solids, independent of various factors.

Contribution

It introduces a semi-phenomenological approach that accounts for finite-dimensional fluctuations, revealing the origin of universal quartic scaling in amorphous solids.

Findings

Universal quartic scaling of excess soft modes explained

Finite-dimensional fluctuations modify mean-field predictions

Pressure and protocol dependence of soft modes accounted for

Abstract

Amorphous solids have excess soft modes in addition to the phonon modes described by the Debye theory. Recent numerical results show that if the phonon modes are carefully removed, the density of state of the excess soft modes exhibit universal quartic scaling, independent of the interaction potential, preparation protocol, and spatial dimensions. We hereby provide a theoretical framework to describe this universal scaling behavior. For this purpose, we extend the mean-field theory to include the effects of finite dimensional fluctuation. Based on a semi-phenomenological argument, we show that mean-field quadratic scaling is replaced by the quartic scaling in finite dimensions. Furthermore, we apply our formalism to explain the pressure and protocol dependence of the excess soft modes.