Coherent and Incoherent Structural Dynamics in Laser-Excited Antimony

TL;DR

This study uses femtosecond electron diffraction and ab initio simulations to simultaneously probe coherent and incoherent electron-phonon interactions in laser-excited antimony, revealing detailed dynamics of phonon excitation and energy transfer.

Contribution

It provides a combined experimental and theoretical analysis of both coherent and incoherent electron-phonon coupling in antimony under laser excitation, with quantitative agreement between simulations and measurements.

Findings

Observation of coherent g phonon mode excitation

Quantification of electron-phonon coupling as a function of electronic temperature

Agreement between ab initio simulations and experimental data

Abstract

We investigate the excitation of phonons in photoexcited antimony and demonstrate that the entire electron-lattice interactions, in particular coherent and incoherent electron-phonon coupling, can be probed simultaneously. Using femtosecond electron diffraction (FED) with high temporal resolution, we observe the coherent excitation of the fully symmetric \Ag\ optical phonon mode via the shift of the minimum of the atomic potential energy surface. Ab initio molecular dynamics simulations on laser excited potential energy surfaces are performed to quantify the change in lattice potential and the associated real-space amplitude of the coherent atomic oscillations. Good agreement is obtained between the parameter-free calculations and the experiment. In addition, our experimental configuration allows observing the energy transfer from electrons to phonons via incoherent electron-lattice scattering events. The electron-phonon coupling is determined as a function of electronic temperature from our DFT calculations and the data by applying different models for the energy-transfer.