Correlation between vibrational anomalies and emergent anharmonicity of local potential energy landscape in metallic glasses

Abstract

The boson peak (BP) is a universal feature in the Raman and inelastic scattering spectra of both disordered and crystalline materials. The current paradigm presents the boson peak as the result of a Ioffe-Regel crossover between ballistic (phonon) and diffusive-type excitations, where the loss of coherence of phonons is described as a purely harmonic process due to structural disorder. This "harmonic disorder" paradigm for the BP has never been challenged or tested at the atomistic level. Here, through a set of atomistically-resolved characterizations of amorphous metallic alloys, we uncover a robust inverse proportionality between the intensity of boson peak and the activation energy of excitations in the potential energy landscape (PEL). Larger boson peak is linked with shallower basins and lower activation barriers and, consequently, with strongly anharmonic sectors of the PEL. Numerical evidence from atomistic simulations indicates that THz atomic vibrations contributing the most to the BP in atomic glasses are strongly anharmonic, as evidenced through very large values of the atomic- and mode-resolved Grüneisen parameter found for the atomic vibrations that constitute the BP. These results provide a direct bridge between the vibrational spectrum and the topology of the PEL in solids, and point towards a new "giant anharmonicity" paradigm for both generic disordered materials and for the phonon-glass problem in emerging materials for energy applications. In this sense, disorder and anharmonicity emerge as the two sides of the same coin.

References in corpus (12)

• Giant Anharmonic Phonon Scattering in PbTe
• Microscopic Mechanisms of Glass-Like Lattice Thermal Transport in Cubic Cu${}_{12}$Sb${}_4$S${}_{13}$ Tetrahedrites
• Hypersound damping in vitreous silica measured by picosecond acoustics
• Fast Dynamics in a Model Metallic Glass-forming Material
• A simple and broadly-applicable definition of shear transformation zones
• Superionic UO2: A Model Anharmonic Crystalline Material
• Emergence of glassy features in halomethane crystals
• Observation of High-frequency Transverse Phonons in Metallic Glasses
• Glassy anomalies in the low-temperature thermal properties of a minimally disordered crystalline solid
• Unified theory of vibrational spectra in amorphous materials
• Anharmonic phonon damping enhances the $T_c$ of BCS-type superconductors
• Disentangling interatomic repulsion and anharmonicity in the viscosity and fragility of glasses

Cited by in corpus (4)

• Anharmonic theory of superconductivity and its applications to emerging quantum materials
• Stringlet Excitation Model of the Boson Peak
• Atomistic mechanisms of dynamics in a two-dimensional dodecagonal quasicrystal
• Transport and relaxation of current-generated nonequilibrium phonons from nonlocal electronic measurements