Selective observation of enantiomeric chiral phonons in α\alpha-quartz

We report anomalous circularly polarized Raman spectra of phonons in right- and left-handed quartzes. The phonon branches splitting from the E-mode at a finite wavenumber were found to be chiral with mutually opposite angular momenta. Our analysis reveals the Raman selection rules for chiral phonons. We also find that the conservation of angular momentum should be satisfied between two photons and one chiral phonon in the Raman process. Furthermore, we experimentally proved that the helicity of phonons with a certain frequency and wavevector should be opposite in the other enantiomer

Boson peak dynamics of natural polymer starch investigated by terahertz time-domain spectroscopy and low-frequency Raman scattering

Terahertz time-domain spectroscopy and low-frequency Raman scattering were performed on the natural polymer starch to investigate the boson peak (BP) dynamics. In the infrared spectrum, the BP was observed at 0.99 THz at the lowest temperature. Compared to the result from a previous study for vitreous glucose, both the frequency of the BP and absorption coefficient show lower values than those of the vitreous glucose. These behaviors originate from the longer correlation length of the medium-range order and lower concentration of hydroxyl groups in the starch. In the Raman spectrum, the BP was observed at 1.1 THz at room temperature, although the BP was not observed around room temperature due to the excess wing of the fast relaxation modes in the infrared spectrum. The temperature dependence of ε″(ν) during the heating process and cooling process shows a hysteresis below 230 K. During the heating process, kinks were observed at 140 K and 230 K. These kinks are attributed to the β-relaxation and the βwet-relaxation, respectively

Formation of metallic cation-oxygen network for anomalous thermal expansion coefficients in binary phosphate glass

ガラスが熱で変形しやすいのはなぜか、原子レベルで一端を解明. 京都大学プレスリリース. 2017-06-01.Understanding glass structure is still challenging due to the result of disorder, although novel materials design on the basis of atomistic structure has been strongly demanded. Here we report on the atomic structures of the zinc phosphate glass determined by reverse Monte Carlo modelling based on diffraction and spectroscopic data. The zinc-rich glass exhibits the network formed by ZnOx (averaged x<4) polyhedra. Although the elastic modulus, refractive index and glass transition temperature of the zinc phosphate glass monotonically increase with the amount of ZnO, we find for the first time that the thermal expansion coefficient is very sensitive to the substitution of the phosphate chain network by a network consisting of Zn-O units in zinc-rich glass. Our results imply that the control of the structure of intermediate groups may enable new functionalities in the design of oxide glass materials