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

The boson peak (BP) is a universal feature in the Raman and inelastic scattering spectra of both disordered and crystalline materials. Here, through a set of atomistically resolved characterizations of metallic glasses, we uncover a robust inverse proportionality between the intensity of the boson peak and the activation energy of excitations in the potential energy landscape (PEL). Larger boson peaks are linked with shallower basins and lower activation barriers and, consequently, with emergent 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 correlated with such emergent anharmonicity of the PEL, 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 amorphous solids.