Inverted nucleation for photoinduced nonequilibrium melting

Area of Science:

• Condensed Matter Physics
• Materials Science
• Physical Chemistry

Background:

• Ultrafast photoinduced melting is key to studying nonequilibrium phase transitions.
• Understanding the interplay between electron dynamics and ionic motion is crucial.
• The energetics and kinetics of photoexcited states influence material transformations.

Purpose of the Study:

• To investigate the role of transient ionic pressure in ultrafast photoinduced melting.
• To elucidate the mechanism of solid-to-liquid transitions under nonequilibrium conditions.
• To establish a fundamental understanding of electron-driven material dynamics.

Main Methods:

• Direct imaging of fluctuating density distributions.
• Two-temperature molecular dynamics simulations to evaluate ionic pressure and Gibbs free energy.
• Experimental verification of simulation results.

Main Results:

• Transient ionic pressure, initiated by photoexcited electrons, governs melting kinetics.
• Ultrafast melting proceeds via a reverse nucleation mechanism with voids as seeds.
• The solid-to-liquid transition in gold is explained by void nucleation facilitated by electron-induced pressure.

Conclusions:

• Photoexcited electron-initiated ionic pressure is the primary driver of ultrafast melting.
• Void nucleation is a critical pathway in electron-driven phase transitions.
• This study provides a foundational understanding for ultrafast nonequilibrium kinetics.