Relaxation timescales and electron-phonon coupling in optically pumped YBa2Cu3O6+x revealed by time-resolved Raman scattering
Relaxation timescales and electron-phonon coupling in optically pumped YBa2Cu3O6+x revealed by time-resolved Raman scattering
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DOI：
10.1103/physrevb.104.l180505
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发表时间：
2020-10
影响因子：
3.7
通讯作者：
N. Pellatz;S. Roy;J-W. Lee;J. Schad;H. Kandel;N. Arndt;C. Eom;A. Kemper;D. Reznik
中科院分区：
文献类型：
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作者：
N. Pellatz;S. Roy;J-W. Lee;J. Schad;H. Kandel;N. Arndt;C. Eom;A. Kemper;D. Reznik
近年来，利用超快激光脉冲驱动材料产生了具有惊人性质的量子物质。然而，通过光激发后的单一性质作为时间的函数来观察这些相提供了有限的图像。利用时间分辨拉曼散射技术直接跟踪了高温超导体YBa $_2$ Cu $_3$ O $_{6.9}$中的热声子和瞬态加热，时间分辨为220 fs。此外，我们利用光激发后拉曼活性顶端氧声子的硬化作为热电子的间接探针，它与热声子在0.5 ps左右达到平衡。基于双温模型的分析表明，温度无关的电子-声子耦合为$\lambda \approx $ 0.8，并且随着温度的升高，电子-声子的非调和性显著增加。为了在铜氧化物中产生更长的非平衡态，必须减少这种非调和性。我们还讨论了根据这些结果最近报道的低掺杂光致超导性的新见解。
Quantum matter with striking properties has recently been generated by driving materials with ultrafast laser pulses. However, observing these phases by following a single property as a function of time after photoexcitation provides a limited picture. We directly tracked hot phonons and transient heating in a high temperature superconductor YBa$_2$Cu$_3$O$_{6.9}$ by time-resolved Raman scattering with time-resolution of 220 fs. In addition, we used the hardening of the Raman-active apical oxygen phonon right after photoexcitation as an indirect probe of hot electrons, which equilibrated with hot phonons around 0.5 ps. Analysis based on the two-temperature model revealed temperature-independent electron-phonon coupling with $\lambda \approx $ 0.8 as well as significant anharmonicity that increased with temperature. It is essential to reduce this anharmonicity to generate longer lived nonequilibrium states in copper oxides. We also discuss new insights into photoinduced superconductivity recently reported at lower doping that follow from these results.