Multiscale phase nucleation driven by photoinduced polarons in a volume-changing material

Area of Science:

• Materials Science
• Condensed Matter Physics
• Photochemistry

Background:

• Ultrafast light control of functional materials is vital for optoelectronic devices.
• Understanding the multiscale dynamics of photoinduced phase transformations is experimentally challenging.
• Ferroelastic charge-transfer Prussian blue analogues are promising materials for light-induced applications.

Purpose of the Study:

• To elucidate the mechanisms of microscopic photoinduced excitations leading to macroscopic phase transformation.
• To track the non-equilibrium dynamics in a ferroelastic charge-transfer Prussian blue analogue using advanced techniques.
• To identify the role of electronic and structural dynamics in triggering phase nucleation.

Main Methods:

• Femtosecond X-ray techniques were employed to probe ultrafast dynamics.
• Time-resolved measurements captured electronic and structural evolution.
• Analysis focused on isolating multiscale dynamics from initial photoexcitation to phase transformation.

Main Results:

• Initial electronic excitation induced reverse Jahn-Teller distortion within 50 fs.
• Intermetallic charge-transfer polarons formed within 200 fs.
• Polarons generated lattice strain, triggering phase nucleation within 60 ps, demonstrating elastically driven cooperativity.

Conclusions:

• Photoinduced polarons are key intermediates in driving macroscopic phase transformations.
• Elastic cooperativity initiated by polarons provides an efficient pathway for generating and stabilizing photoinduced phases.
• This mechanism is relevant for various volume-changing materials with potential optoelectronic applications.