Statistics and Properties of Low-Frequency Vibrational Modes in Structural Glasses

Low-frequency vibrational modes play a central role in determining various basic properties of glasses, yet their statistical and mechanical properties are not fully understood. Using extensive numerical simulations of several model glasses in three dimensions, we show that in systems of linear size L sufficiently smaller than a crossover size L_D, the low-frequency tail of the density of states follows D(ω)∼ω⁴ up to the vicinity of the lowest Goldstone mode frequency. We find that the sample-to-sample statistics of the minimal vibrational frequency in systems of size L<L_D is Weibullian, with scaling exponents in excellent agreement with the ω⁴ law. We further show that the lowest-frequency modes are spatially quasilocalized and that their localization and associated quartic anharmonicity are largely frequency independent. The effect of preparation protocols on the low-frequency modes is elucidated, and a number of glassy length scales are briefly discussed.