Nonadiabatic generation of coherent phonons

TL;DR

This paper uses time-dependent density functional theory to study how intense laser pulses generate coherent optical phonons in antimony, highlighting nonadiabatic effects and comparing with simpler dielectric models.

Contribution

It applies TDDFT to model nonadiabatic coherent phonon generation in antimony, providing insights into the process and comparing with dielectric models.

Findings

TDDFT captures qualitative features of coherent phonons in Sb.

Nonadiabatic coupling is crucial for phonon generation in this material.

Simple dielectric models are compared with TDDFT results.

Abstract

The time-dependent density functional theory (TDDFT) is the leading computationally feasible theory to treat excitations by strong electromagnetic fields. Here the theory is applied to coherent optical phonon generation produced by intense laser pulses. We examine the process in the crystalline semimetal antimony (Sb), where nonadiabatic coupling is very important. This material is of particular interest because it exhibits strong phonon coupling and optical phonons of different symmetries can be observed. The TDDFT is able to account for a number of qualitative features of the observed coherent phonons, despite its unsatisfactory performance on reproducing the observed dielectric functions of Sb. A simple dielectric model for nonadiabatic coherent phonon generation is also examined and compared with the TDDFT calculations.