Ultrafast Optically Induced Perturbation of Oxygen Octahedral Rotations in Multiferroic BiFeO₃ Thin Films

Area of Science:

• Materials Science
• Condensed Matter Physics
• Solid State Chemistry

Background:

• Functional properties of complex oxides depend on structural distortions.
• Ultrafast optical excitations offer precise control over material structures.

Purpose of the Study:

• Investigate the impact of ultrafast optical excitation on the structural dynamics of multiferroic BiFeO3.
• Establish the link between lattice expansion and oxygen octahedral rotation (OOR) patterns.
• Explore ultrafast control of functional properties in complex oxides.

Main Methods:

• Time-resolved X-ray free-electron laser (XFEL) diffraction with femtosecond resolution.
• Ultrafast optical excitation.
• Density functional theory (DFT) calculations.

Main Results:

• Above-bandgap optical excitation induced lattice expansion in BiFeO3.
• This expansion led to a distortion of the oxygen octahedral rotation (OOR) pattern.
• Experimental results showed continuous coupling between OOR and strain, consistent with DFT predictions.

Conclusions:

• Ultrafast optical excitation can precisely manipulate OOR patterns in multiferroic BiFeO3.
• This provides a pathway for controlling ferroelectricity and magnetism in complex oxides.
• The demonstrated approach is applicable to a broader range of materials.