Low-frequency hybridized excess vibrations of two-dimensional glasses

Abstract

Abstract One hallmark of glasses is the existence of excess vibrational modes at low frequencies $\omega$ beyond the Debye's prediction. Numerous studies suggest that understanding low-frequency excess vibrations could help gain insight into the anomalous mechanical and thermodynamic properties of glasses. However, it is still under intensive debate on the frequency dependence of the population of low-frequency excess vibrations. In particular, excess modes could hybridize with phonon-like modes, and the density of hybridized excess modes has been reported to follow $D_{\rm exc}(\omega) \sim \omega^{2}$ in 2D glasses with an inverse-power-law potential. Yet, it remains to check the universality of the quadratic scaling since recent work suggested that the interaction potentials could influence the scaling of vibrational spectrum. Here, we extend the universality of the quadratic scaling for hybridized excess modes in 2D to glasses with potentials ranging from the purely repulsive soft-core interaction to the hard-core one with both repulsion and attraction as well as to glasses with significant difference in the density or the interparticle repulsion. Moreover, we observe that the number of hybridized excess modes exhibits a decrease in glasses with higher density or steeper interparticle repulsion, which is accompanied by a suppression in the strength of the sound attenuation. Our results indicate that the density bears some resemblance to the repulsive steepness of the interaction in influencing low-frequency properties.