Microscopic description of displacive coherent phonons
Microscopic description of displacive coherent phonons
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DOI：
10.1103/physrevb.99.035131
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发表时间：
2019-01-16
影响因子：
3.7
通讯作者：
Paul, I
中科院分区：
文献类型：
--
作者：
Lakehal, M.;Paul, I
我们开发了一种基于哈密顿量的激光泵浦诱导位移相干声子的微观描述。该理论捕获了声子激发对电子流体的反馈，这在最先进的唯象学公式中是缺失的。我们证明，即使声子运动是谐波的，这种反馈也会导致短时间尺度的啁啾。在很长一段时间内，这种反馈在振荡信号中表现为有限相位。我们将该理论应用于 BaFe2As2，解释了最近实验中报告的振荡信号的相位起源，并且我们预测系统将在更大的能量密度下表现出红移啁啾。我们的理论还开启了从相干声子动力学中提取平衡信息的可能性。
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.