Anisotropic light-electron-phonon coupling and ultrafast carrier separation in ferroelectric BaTiO$_3$

TL;DR

This study reveals that ferroelectric BaTiO₃ exhibits polarization-dependent electron-phonon interactions and ultrafast carrier dynamics, which are crucial for advancing ultrafast electronic and solar energy devices.

Contribution

It demonstrates polarization-sensitive light-electron-phonon coupling and visualizes photo-excited carrier motion in BaTiO₃ using ultrafast electron diffraction and electrometry.

Findings

Electrons relax faster into phonons when electric field aligns with polarization

Ultrafast electron electrometry visualizes electron-hole pair motion

Light response depends on ferroelectric polarization orientation

Abstract

Ferroelectric materials with built-in electric fields are useful for ultrafast electronics and solar cells. Using ultrafast electron diffraction, we here report that ferroelectric BaTiO$_3$ reacts to light with a polarization-sensitive electron-phonon coupling. Excited electrons relax faster into phonons and temperature when the optical electric field aligns to the ferroelectric polarization. Also, ultrafast electron electrometry visualizes the motion of photo-excited electron-hole pairs in presence of the ferroelectric field.