Broad-band ellipsometry study of the anisotropic dielectric response of YAlO3

TL;DR

This study uses broad-band ellipsometry to analyze the anisotropic dielectric properties of YAlO3 across a wide spectral range, identifying phonon modes, observing negative refraction, and examining temperature effects.

Contribution

It provides comprehensive experimental data on YAlO3's dielectric tensor, including phonon modes and negative refraction, filling gaps in the understanding of its optical anisotropy.

Findings

Identified all 25 infrared active phonon modes.

Observed negative refraction near an anisotropic phonon.

Determined temperature dependence of phonon parameters.

Abstract

We present a broad band (THz to UV) ellipsometry study of the anisotropic dielectric response of the orthorhombic perovskite YAlO3. The ellipsometric measurements have been performed on YAlO3 crystals with three different surface cuts and for six high symmetry configurations of the crystal axes with respect to the plane of incidence of the photons. The obtained data are presented in terms of the Mueller Matrix elements N, C, and S and their features are analyzed and discussed with respect to the anisotropy of the dielectric response tensor. In particular, in the infrared range we have identified all 25 infrared active phonon modes that have been predicted from theoretical studies. We also discuss a negative refraction effect that naturally occurs in the vicinity of an anisotropic longitudinal-optical phonon. Moreover, we have determined the temperature dependence of the phonon parameters between 10 and 330 K. The dielectric response above the phonon range, from about 0.1 to 6.5 eV, is shown to be featureless and characteristic of an insulator with a large band gap above 6.5 eV and is well described by anisotropic Cauchy model.