Christopher J. Winta, Martin Wolf, and Alexander Paarmann:
Phys. Rev. B 99 (14), 144308 (2019), pp.7;
arXiv:1902.03072 [cond-mat.mtrl-sci] (2019), pp. 7;
DOI: arXiv:1902.03072 [cond-mat.mtrl-sci]
We report the infrared dielectric properties of a-quartz in the temperature range from 1.5 K to 200 K. Using an infrared free-electron laser, far-infrared reflectivity spectra of a single crystal y-cut were acquired along both principal axes, under two different incidence angles, in S- and P-polarization. These experimental data have been fitted globally for each temperature with a multioscillator model, allowing to extract frequencies and damping rates of the ordinary and extraordinary, transverse and longitudinal optic phonon modes, and hence the temperature-dependent dispersion of the infrared dielectric function. The results are in line with previous high-temperature studies, allowing for a parametrized description of all temperature-dependent phonon parameters and the resulting dielectric function from 1.5 K up to the a-ß-phase transition temperature, TC=846 K. Using these data, we predict remarkably high quality factors for polaritons in a-quartz's hyperbolic spectral region at low temperatures.
The original publication is available by link DOI: 10.1103/PhysRevB.99.144308