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Excitations glasses

In amorphous materials, groups of particles can rearrange locally into a new stable configuration. Such elementary excitations are key as they determine the response to external stresses [1], as well as to thermal and quantum fluctuations [2]. Yet, understanding what controls their geometry remains a challenge. We build a scaling description of the geometry and energy of low-energy excitations in terms of the distance to an instability, as predicted for instance at the dynamical transition in mean field approaches of supercooled liquids [3]. We successfully test our predictions in ultrastable computer glasses, with a gapped and ungapped (regular) spectrum. Our approach explains why excitations become less extended, with a higher energy and displacement scale upon cooling.

Selected publications

[1]

W. Ji, M. Popović, T.W.J. de Geus, E. Lerner, and M. Wyart. Theory for the density of interacting quasilocalized modes in amorphous solids. Phys. Rev. E, 99(2):023003, 2019. arXiv:1806.01561, doi:10.1103/PhysRevE.99.023003.

[2]

W. Ji, T.W.J. de Geus, M. Popović, E. Agoritsas, and M. Wyart. Thermal origin of quasilocalized excitations in glasses. Phys. Rev. E, 102(6):062110, 2020. arXiv:1912.10537, doi:10.1103/PhysRevE.102.062110.

[3]

W. Ji, T.W.J. de Geus, E. Agoritsas, and M. Wyart. Mean-field description for the architecture of low-energy excitations in glasses. Phys. Rev. E, 105(4):044601, 2022. arXiv:2106.13153, doi:10.1103/PhysRevE.105.044601.