Uniaxial stress studies of H centers in In$_{\mathrm{2}}$O$_{\mathrm{3}}$

In$_{\mathrm{2}}$O$_{\mathrm{3}}$ single crystals have been grown for our experiments that are sufficiently large to make possible IR absorption measurements in conjunction with uniaxial stress. The introduction of H produces an IR line at 3306 cm$^{\mathrm{-1}}$ that has been assigned to the OH stretching mode of an interstitial H shallow donor in In$_{\mathrm{2}}$O$_{\mathrm{3}}$ [1]. We have performed IR absorption experiments in which the splitting of the 3306 cm$^{\mathrm{-1}}$ line under stresses applied at low temperatures provides information about the symmetry of the OH center. Stress measurements made at elevated temperatures reveal a stress-induced dichroism that provides information about the motion of hydrogen associated with the 3306 cm$^{\mathrm{-1}}$ center. [1] W. Yin \textit{et al}., Phys. Rev. B \textbf{91}, 075208 (2015).