title: Heterogeneous shear elasticity of glasses: the origin of the boson peak.
abstract: The local elasticity of glasses is known to be inhomogeneous on a microscopic scale compared to that of crystalline materials. Their vibrational spectrum strongly deviates from that expected from Debye's elasticity theory: The density of states deviates from Debye's law, the sound velocity shows a negative dispersion in the boson-peak frequency regime and there is a strong increase of the sound attenuation near the boson-peak frequency. By comparing a mean-field theory of shear-elastic heterogeneity with a large-scale simulation of a soft-sphere glass we demonstrate that the observed anomalies in glasses are caused by elastic heterogeneity. By observing that the macroscopic bulk modulus is frequency independent we show that the boson-peak-related vibrational anomalies are predominantly due to the spatially fluctuating microscopic shear stresses. It is demonstrated that the boson-peak arises from the steep increase of the sound attenuation at a frequency which marks the transition from wave-like excitations to disorder-dominated ones.
authors.affiliation: Dipartimento di Fisica, Universitá di Roma La Sapienza, Roma, Italy.
authors.forename: Alessia
authors.initials: A
authors.lastname: Marruzzo
authors.forename: Walter
authors.initials: W
authors.lastname: Schirmacher
authors.forename: Andrea
authors.initials: A
authors.lastname: Fratalocchi
authors.forename: Giancarlo
authors.initials: G
authors.lastname: Ruocco