Optical spectroscopy on the photo-response in multiferroic BiFeO$_3$ at high pressure

TL;DR

This study investigates how high pressure affects light-induced absorption features in BiFeO$_3$, revealing their connection to the polar phase and their irreversible disappearance after a phase transition.

Contribution

It provides new insights into the pressure-dependent optical properties and phase behavior of BiFeO$_3$, linking photo-induced effects to structural phases.

Findings

Light-induced absorption features shift with pressure, following crystal field excitations.

Features disappear after the structural phase transition at ~3.5 GPa.

Disappearance of features is irreversible upon pressure release.

Abstract

The pressure dependence of light-induced effects in single-crystalline BiFeO$_3$ is studied by optical spectroscopy. At low pressures, we observe three light-induced absorption features with energies just below the two crystal field excitations and the absorption onset, respectively. These absorption features were previously ascribed to excitons, possibly connected with the ultra-fast photostriction effect in BiFeO$_3$. The pressure-induced redshift of the absorption features follows the pressure dependence of the corresponding crystal field excitations and absorption onset, suggesting the link between them. Above the structural phase transition at $P_{\mathrm{c1}}\approx{}3.5$ GPa the three absorption features disappear, suggesting their connection to the polar phase in BiFeO$_3$. The pressure-induced disappearance of the photo-induced features is irreversible upon pressure release.