A Microscopic Description of Displacive Coherent Phonons

We develop a Hamiltonian-based microscopic description of laser pump induced displacive coherent phonons. The theory captures the feedback of the phonon excitation upon the electronic fluid, which is missing in the state-of-the-art phenomenological formulation. We show that this feedback leads to ch...

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Bibliographic Details
Published in:arXiv.org 2019-01
Main Authors: Lakehal, M, Paul, I
Format: Article
Language:English
Subjects:
Coherence
Feedback
Fluence
Phonons
State of the art
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Summary:We develop a Hamiltonian-based microscopic description of laser pump induced displacive coherent phonons. The theory captures the feedback of the phonon excitation upon the electronic fluid, which is missing in the state-of-the-art phenomenological formulation. We show that this feedback leads to chirping at short time scales, even if the phonon motion is harmonic. At long times this feedback appears as a finite phase in the oscillatory signal. We apply the theory to BaFe\(_2\)As\(_2\), explain the origin of the phase in the oscillatory signal reported in recent experiments, and we predict that the system will exhibit red-shifted chirping at larger fluence. Our theory also opens the possibility to extract equilibrium information from coherent phonon dynamics.
ISSN:2331-8422
DOI:10.48550/arxiv.1806.00021