We report a comprehensive study of ultrafast carrier dynamics in single crystals of multiferroic BiFeO3. 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 BiFeO3, its intrinsic nature results in carrier relaxation similar to that observed in bulk semiconductors.

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The dynamics discussed for electrons generally also applies to holes throughout the text.

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We estimate this change using room temperature parameters and from the difference between transient reflectivity traces for different photon energies near 3 ps.

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