Echoes from Anharmonic Normal Modes in Model Glasses

Abstract

Glasses display a wide array of nonlinear acoustic phenomena at temperatures $T\lesssim 1$ K. This behavior has traditionally been explained by an ensemble of weakly-coupled, two-level tunneling states, a theory that is also used to describe the thermodynamic properties of glasses at low temperatures. One of the most striking acoustic signatures in this regime is the existence of phonon echoes, a feature that has been associated with two-level systems with the same formalism as spin echoes in NMR. Here we report the existence of distinctly different type of acoustic echo in classical models of glassy materials. Our simulations consist of finite-ranged, repulsive spheres and also particles with attractive forces using Lennard-Jones interactions. We show that these echoes are due to anharmonic, weakly-coupled vibrational modes, and perhaps provide an alternative explanation for the phonon echoes observed in glasses at low temperatures.

12 pages, 11 figures

References in corpus (5)

• Jamming at Zero Temperature and Zero Applied Stress: the Epitome of Disorder
• Excess Vibrational Modes and the Boson Peak in Model Glasses
• Energy transport in jammed sphere packings
• Predicting plasticity with soft vibrational modes: from dislocations to glasses
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Cited by in corpus (5)

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