Anisotropy of the infrared-active phonon modes in the mono-domain state of tetragonal SrTiO3 (110)

TL;DR

This study uses infrared and terahertz ellipsometry to analyze phonon mode anisotropy in SrTiO3 (110), revealing how uniaxial stress can induce a mono-domain state and intrinsic phonon splitting below 105 K.

Contribution

It demonstrates how moderate uniaxial stress can create a mono-domain state in SrTiO3 (110) and reports the intrinsic phonon mode splitting in this state.

Findings

Mono-domain state achieved with 2.3 MPa stress

Anisotropy of R-mode oscillator strength as domain indicator

Intrinsic phonon splitting observed below T*

Abstract

With infrared and terahertz ellipsometry we investigated the anisotropy of the infrared active phonon modes in SrTiO3 (110) single crystals in the tetragonal state below the so-called antiferrodistortive transition at T* = 105 K. In particular, we show that the anisotropy of the oscillator strength of the so-called R-mode, which becomes weakly infrared active below T*, is a valuable indicator for the orientation of the structural domains. Our results reveal that a mono-domain state with the tetragonal axis (c-axis) parallel to the [001] direction can be created by applying a moderate uniaxial stress of about 2.3 MPa along the [1-10] direction (with a mechanical clamp). The resulting, intrinsic splitting of the infrared-active phonon modes is reported.