Microscopic description of displacive coherent phonons

  title={Microscopic description of displacive coherent phonons},
  author={Massil Lakehal and Indranil Paul},
  journal={Physical Review B},
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… 
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