Optical spectroscopy on the photo-response in multiferroic BiFeO3 at high pressure

Abstract

The pressure dependence of light-induced effects in single-crystalline BiFeO3 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 ultrafast photostriction effect in BiFeO3. 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 Pc1≈3.5GPa, the three absorption features disappear, suggesting their connection to the polar phase in BiFeO3. The pressure-induced disappearance of the photoinduced features is irreversible upon pressure release.