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:Physical review. B 2019-01, Vol.99 (3), p.1, Article 035131
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 timescales, 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 BaFe2As2, explain the origin of the phase in the oscillatory signal reported in recent experiments, and we predict that the system will exhibit redshifted chirping at larger fluence. Our theory also opens the possibility to extract equilibrium information from coherent phonon dynamics.
ISSN:2469-9950
2469-9969
DOI:10.1103/PhysRevB.99.035131