超导YBCO中的局域振动
Localised vibrations in superconducting YBCO revealed by ultra-fast optical coherent spectroscopy
摘要：
铜氧化物中声子与高能电子激发的相互作用及其在超导机制中的作用至今仍有争议。在这里，我们使用相干振动时域光谱与密度泛函和动力学平均场论计算建立一个直接的联系之间的c轴声子模式和平面内的电子电荷激发在最佳掺杂的YBCO。非平衡拉曼张量测量的宽带相干声子的响应在泵浦-探测实验和定性描述我们的模型使用DFT冻结声子近似加上单带DMFT占电子相关。我们的实验和理论研究的主要成果是建立面外铜离子位移和面内电子关联之间的联系，并估计在几个单位细胞的相关声子模式的相关长度。这里介绍的方法可以帮助揭示几种强相关材料中不同性质的波动和空间相关性之间的复杂相互作用。
英文摘要：
The interaction between phonons and high-energy excitations of electronic origin in cuprates and their role in the superconducting mechanisms is still controversial. Here we use coherent vibrational time-domain spectroscopy together with density functional and dynamical mean-field theory calculations to establish a direct link between the c-axis phonon modes and the in-plane electronic charge excitations in optimally doped YBCO. The non-equilibrium Raman tensor is measured by means of the broadband 'coherent-phonon' response in pump-probe experiments and is qualitatively described by our model using DFT in frozen phonon approximation plus single band DMFT to account for the electronic correlations. The major outcome of our experimental and theoretical study is to establish the link between out-of-plane copper ions displacements and the in-plane electronic correlations, and to estimate at few unit cells the correlation length of the associated phonon mode. The approach introduced here could help revealing the complex interplay between fluctuations of different nature and spatial correlation in several strongly-correlated materials.
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