Low-energy excitation in As2S3 glass studied by inelastic X-ray scattering

Abstract

The low-energy excitation of As2S3 glass was measured for the first time by high-resolution inelastic X-ray scattering to obtain an additional insight into the Boson peak. The experiments were performed at room temperature at Q=1.5–63.6nm−1 and ω=−40–50meV. Besides an acoustic-like collective mode in the low-Q region, the low-energy excitation was clearly observed above 20nm−1 around 3meV, whose intensity increases with increasing Q and exhibits a maximum at 39nm−1 in coincidence with the third peak of the structural factor S(Q). The observations suggest that the low-energy excitation of As2S3 glass at Q>20nm−1 may originate from localized vibrational soft modes associated with the dynamical correlation of S atoms with the nearest-neighboring As atoms.