Ultrafast carrier dynamics and radiative recombination in multiferroic BiFeO$_{3}$

TL;DR

This study investigates ultrafast carrier relaxation in multiferroic BiFeO$_{3}$ using femtosecond spectroscopy, revealing electron-phonon interactions and radiative recombination unaffected by magnetic transitions, similar to semiconductors.

Contribution

It provides the first detailed analysis of ultrafast carrier dynamics in BiFeO$_{3}$, highlighting the role of electron-phonon coupling and radiative processes in this multiferroic material.

Findings

Electron relaxation occurs within ~1 ps via electron-phonon coupling.

Radiative recombination dominates electron decay after initial relaxation.

Carrier dynamics are similar to those in bulk semiconductors despite multiferroic order.

Abstract

We report a comprehensive study of ultrafast carrier dynamics in single crystals of multiferroic BiFeO$_{3}$. Using femtosecond optical pump-probe spectroscopy, we find that the photoexcited electrons relax to the conduction band minimum through electron-phonon coupling with a $\sim$1 picosecond time constant that does not significantly change across the antiferromagnetic transition. Photoexcited electrons subsequently leave the conduction band and primarily decay via radiative recombination, which is supported by photoluminescence measurements. We find that despite the coexisting ferroelectric and antiferromagnetic orders in BiFeO$_{3}$, the intrinsic nature of this charge-transfer insulator results in carrier relaxation similar to that observed in bulk semiconductors.