Ultrafast carrier dynamics and radiative recombination in multiferroic BiFeO ₃

We report a comprehensive study of ultrafast carrier dynamics in single crystals of multiferroic BiFeO ₃. Using degenerate femtosecond optical pump-probe spectroscopy, we find that the photoexcited electrons relax to the conduction band minimum through electron-phonon coupling with a ∼1 ps time constant that does not significantly change across the antiferromagnetic transition. Electrons subsequently leave the conduction band and primarily decay via radiative recombination on a nanosecond timescale, as supported by photoluminescence measurements. We find that despite the coexisting ferroelectric and antiferromagnetic orders in BiFeO ₃, its intrinsic nature results in carrier relaxation similar to that observed in bulk semiconductors.