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 α(ν)/ν 2 [α(ν) 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 C IR (ν) of the vitreous glucose behaves linearly on frequency which deviates from Taraskin

We study collective phonon excitations in SrTiO3 by low-frequency light scattering. We employ extended thermodynamics for phonon gas to construct a theoretical spectral function that is applicable regardless of local thermal equilibrium. Our analysis reveals the temperature dependence of tauN, the relaxation time for the momentum-conserving phonon collisions (normal processes), in SrTiO3. These results indicate that the previously reported anomalous soundlike spectrum originates from second sound, which is a wavelike propagation of heat.

Ultrafast control of magnets using femtosecond light pulses attracts interest regarding applications and fundamental physics of magnetism. Antiferromagnets are promising materials with magnon frequencies extending into the terahertz range. Visible or near-infrared light interacts mainly with the electronic orbital angular momentum. In many magnets, however, in particular with iron-group ions, the orbital momentum is almost quenched by the crystal field. Thus, the interaction of magnons with light is hampered, because it is only mediated by weak unquenching of the orbital momentum by spin–orbit interactions. Here we report all-optical excitation of magnons with frequencies up to 9 THz in antiferromagnetic CoO with an unquenched orbital momentum. In CoO, magnon modes are coupled oscillations of spin and orbital momenta with comparable amplitudes. We demonstrate excitations of magnon modes by directly coupling light with electronic orbital angular momentum, providing possibilities to develop magneto-optical devices operating at several terahertz with high output-to-input ratio.

We report the high-resolution and broadband light-scattering spectroscopy of a single crystal of a prototypical relaxor ferroelectric, Pb(Mg(1/3)Nb(2/3))O(3). A self-similar broad central peak, whose intensity is expressed as I(ω) [Symbol: see text] ω(α) has been observed, indicating the presence of a fractal in the crystal. A strong correspondence exists between the temperature dependence of the exponent α and that of the reported behaviors of polar nanoregions. The estimated fractal dimension (d(f) ≈ 2.6) at low temperatures clearly indicates a percolation transition of the polar nanoregions at around 240 K.