Thermal origin of quasi-localised excitations in glasses

Abstract

Key aspects of glasses are controlled by the presence of excitations in which a group of particles can rearrange. Surprisingly, recent observations indicate that their density is dramatically reduced and their size decreases as the temperature of the supercooled liquid is lowered. Some theories predict these excitations to cause a gap in the spectrum of quasi-localised modes of the Hessian that grows upon cooling, while others predict a pseudo-gap $D_L(\omega )\sim {\omega }^{\alpha }$. To unify these views and observations, we generate glassy configurations of controlled gap magnitude ${\omega }_c$ at temperature $T=0$, using so-called `breathing' particles, and study how such gapped states respond to thermal fluctuations. We find that \textit{(i)}~the gap always fills up at finite $T$ with $D_L(\omega )\approx A_4(T){\omega }^4$ and $A_4\sim \exp (-E_a/T)$ at low $T$, \textit{(ii)}~$E_a$ rapidly grows with ${\omega }_c$, in reasonable agreement with a simple scaling prediction $E_a\sim {\omega }_c^4$ and \textit{(iii)}~at larger ${\omega }_c$ excitations involve fewer particles, as we rationalise, and eventually become string-like. We propose an interpretation of mean-field theories of the glass transition, in which the modes beyond the gap act as an excitation reservoir, from which a pseudo-gap distribution is populated with its magnitude rapidly decreasing at lower $T$. We discuss how this picture unifies the rarefaction as well as the decreasing size of excitations upon cooling, together with a string-like relaxation occurring near the glass transition.

References in corpus (38)

• String-like Clusters and Cooperative Motion in a Model Glass-Forming Liquid
• Decoherence in Josephson Qubits from Dielectric Loss
• Supercooled Liquids for Pedestrians
• Theory of Structural Glasses and Supercooled Liquids
• Effects of compression on the vibrational modes of marginally jammed solids
• Models and algorithms for the next generation of glass transition studies
• Anharmonicity, vibrational instability and Boson peak in glasses
• A random critical point separates brittle and ductile yielding transitions in amorphous materials
• The Shapes of Cooperatively Rearranging Regions in Glass Forming Liquids
• Subextensive Scaling in the Athermal, Quasistatic Limit of Amorphous Matter in Plastic Shear Flow
• Continuum limit of the vibrational properties of amorphous solids
• Statistics and properties of low-frequency vibrational modes in structural glasses
• Low-frequency vibrational modes of stable glasses
• Vibrational instability, two-level systems and Boson peak in glasses
• Bosonic Excitations in Random Media
• Suppression of tunneling two-level systems in ultrastable glasses of indomethacin
• On the density of shear transformation zones in amorphous solids
• A universal origin for secondary relaxations in supercooled liquids and structural glasses
• Pinching a glass reveals key properties of its soft spots
• The Intrinsic Quantum Excitations of Low Temperature Glasses
• A stability-reversibility map unifies elasticity, plasticity, yielding and jamming in hard sphere glasses
• Elasto-plastic description of brittle failure in amorphous materials
• Does a growing static length scale control the glass transition?
• Efficient swap algorithms for molecular dynamics simulations of equilibrium supercooled liquids
• Spatial structure of quasi-localized vibrations in nearly jammed amorphous solids
• Depletion of two-level systems in ultrastable computer-generated glasses
• Fast generation of ultrastable computer glasses by minimization of an augmented potential energy
• A characteristic energy scale in glasses
• Effect of instantaneous and continuous quenches on the density of vibrational modes in model glasses
• Theory for Swap Acceleration near the Glass and Jamming Transitions
• Soft Modes, Localization and Two-Level Systems in Spin Glasses
• Mean field theory of the swap Monte Carlo algorithm
• Nature of excitations and defects in structural glasses
• Mechanical noise dependent Aging and Shear Banding behavior of a mesoscopic model of amorphous plasticity
• On Variational Arguments for Vibrational Modes near Jamming
• On the origine of the Boson peak
• Theory for the density of interacting quasi-localised modes in amorphous solids
• The Random First-Order Transition Theory of Glasses: a critical assessment

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• Low-frequency excess vibrational modes in two-dimensional glasses
• Mean-field model of interacting quasilocalized excitations in glasses
• Disordered crystals reveal soft quasilocalized glassy excitations
• Density of States below the First Sound Mode in 3D Glasses
• Delocalization transition in low energy excitation modes of vector spin glasses
• Mean-field description for the architecture of low-energy excitations in glasses
• Low-Frequency Vibrational States in Ideal Glasses with Random Pinning
• Local Plastic Response and Slow Heterogeneous Dynamics of Supercooled Liquids
• Variability of mesoscopic mechanical disorder in disordered solids
• Low energy excitations of mean-field glasses
• Soft modes in vector spin glass models on sparse random graphs
• Brittle to ductile transitions in glasses: Roles of soft defects and loading geometry