# Nature of excitations and defects in structural glasses

## TL;DR

This paper investigates the nature of defects and excitations in three-dimensional structural glasses, revealing a transition from collective to localized excitations as density increases, which advances understanding of glassy materials across different regimes.

## Contribution

It provides a comprehensive analysis of defect types and energy landscapes in a microscopic model, connecting microscopic excitations to macroscopic glass properties.

## Key findings

- All glasses have a rough energy landscape with hierarchical barriers.
- Collective excitations dominate in the jamming regime.
- Localized defects become prevalent at higher densities.

## Abstract

The nature of defects in amorphous materials, analogous to vacancies and dislocations in crystals, remains elusive. Here we explore their nature in a three-dimensional microscopic model glass-former which describes granular, colloidal, atomic and molecular glasses by changing the temperature and density. We find that all glasses evolve in a very rough energy landscape, with a hierarchy of barrier sizes corresponding to both localized and delocalized excitations. Collective excitations dominate in the jamming regime relevant for granular and colloidal glasses. By moving gradually to larger densities describing atomic and molecular glasses, the system crosses over to a regime dominated by localized defects and relatively simpler landscapes. We quantify the energy and temperature scales associated to these defects and their evolution with density. Our result pave the way to a systematic study of low-temperature physics in a broad range of physical conditions and glassy materials.