Boson peak dynamics of glassy glucose studied by integrated terahertz-band spectroscopy

TL;DR

This study investigates the boson peak dynamics in vitreous glucose using terahertz spectroscopy, revealing a universal resonance behavior below the peak and proposing a new light-vibration coupling coefficient that challenges existing models.

Contribution

The paper introduces the relative light-vibration coupling coefficient (RCC) derived from combined spectra, providing new insights into boson peak dynamics and light-vibration interactions in glassy glucose.

Findings

Boson peak observed around 1.1 THz in vitreous glucose.

The RCC behaves linearly with frequency, deviating from Taraskin's model.

Discontinuity in transverse sound velocity suggests coupling between acoustic and flattened modes.

Abstract

We performed terahertz time-domain spectroscopy, low-frequency Raman scattering, and Brillouin light scattering on vitreous glucose to investigate the boson peak (BP) dynamics. In the spectra of {\alpha}({\nu})/{\nu}2 [{\alpha}({\nu}) is the absorption coefficient], the BP is clearly observed around 1.1 THz. Correspondingly, the complex dielectric constant spectra show a universal resonancelike behavior only below the BP frequency. As an analytical scheme, we propose the relative light-vibration coupling coefficient (RCC), which is obtainable from the combination of the far-infrared and Raman spectra. The RCC reveals that the infrared light-vibration coupling coefficient CIR({\nu}) of the vitreous glucose behaves linearly on frequency which deviates from Taraskin's model of CIR({\nu}) = A + B{\nu}2 [S. N. Taraskin et al., Phys. Rev. Lett. 97, 055504 (2006)]. The linearity of CIR({\nu}) might require modification of the second term of the model. The measured transverse sound velocity shows an apparent discontinuity with the flattened mode observed in the inelastic neutron scattering study [N. Violini et al., Phys. Rev. B 85, 134204 (2012)] and suggests a coupling between the transverse acoustic and flattened modes.