Local fields reveal atomic-scale nonadiabatic carrier-phonon dynamics.

Area of Science:

• Materials Science
• Quantum Mechanics
• Solid-State Physics

Background:

• Nonadiabatic carrier-lattice interactions are crucial for energy transfer in materials.
• Understanding these interactions at the atomic scale is vital for advancing microelectronics.
• Electron-phonon coupling significantly influences material properties and performance.

Purpose of the Study:

• To investigate ultrafast carrier-lattice dynamics in titanium-carbide MXenes.
• To elucidate the role of nonadiabatic electron-phonon coupling in material relaxation processes.
• To establish a framework for probing and controlling these interactions with site and orbital specificity.

Main Methods:

• Combined attosecond core-level transient absorption spectroscopy with many-body theory.
• Utilized phonon-driven changes in carrier localization to modulate local field effects (LFEs).
• Analyzed carrier-, site-, and orbital-specific absorption signatures.

Main Results:

• Identified nonadiabatic electron-phonon coupling as the driver of ultrafast relaxations.
• LFEs provided sensitive fingerprints of electron-phonon coupling strength across the phonon spectrum.
• Observed a breakdown of the Born-Oppenheimer approximation: electrons lagged lattice oscillations by 32 ± 8 fs, while holes responded almost instantaneously (7 ± 7 fs).

Conclusions:

• Established a novel framework for probing and controlling nonadiabatic carrier-phonon interactions.
• Demonstrated the ability to achieve orbital and site specificity in analyzing these interactions.
• Provided fundamental insights into energy transfer mechanisms limiting microelectronic performance.