Extended and localized vibrations models in disordered systems

TL;DR

This paper investigates vibrational localization in disordered systems, revealing unique universality classes, scaling behaviors, and the relationship between boson peaks and localization phenomena in glasses and media.

Contribution

It demonstrates that vibrational modes in disordered lattices form a different universality class than electrons, with extended eigenvectors in two dimensions and specific scaling laws near the transition.

Findings

Eigenvectors are extended even in two dimensions.

The correlation exponent does not diverge at the transition.

Boson peaks are observed in both 2D and 3D systems.

Abstract

We discuss vibrational localization problems in glasses and disordered media in this paper. It is claimed that the essence of the localization problem is already observed in disordered lattice models. These kinds of vibrations belong to a different universality class than bonded electrons. Specifically, The eigenvectors are extended even in two dimensions. Moreover, the correlation exponent does not diverge in the transition from localized to delocalized states. Furthermore, the volume of the extended states is scaled according to the distance from the transition as $V\sim |\omega-\omega_c| L^d$. Interestingly, boson peaks can be observed in the density of states in both two and three dimensions. We studied the eigenstates of this problem and analyzed the scattering effects in these lattices. Importantly, we found that in two dimensions the boson peak, the localization edge, and the beginning of anomalous scattering are at the same frequency. In three dimensions, however, there are three separate regions: (1) localized, (2) weakly scattered, and (3) anomalously scattered. Finally, we discuss the relevance of this study to actual experiments and glasses.