Detecting electron-phonon coupling during photoinduced phase transition
Detecting electron-phonon coupling during photoinduced phase transition
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DOI：
10.1103/physrevb.103.l121105
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发表时间：
2020-02
期刊：
影响因子：
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通讯作者：
Takeshi Suzuki;Y. Shinohara;Yangfan Lu;M. Watanabe;Jiadi Xu;K. Ishikawa;H. Takagi;M. Nohara;N. Katayama;H. Sawa;M. Fujisawa;T. Kanai;J. Itatani;T. Mizokawa;Shik Shin;K. Okazaki
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文献类型：
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作者：
Takeshi Suzuki;Y. Shinohara;Yangfan Lu;M. Watanabe;Jiadi Xu;K. Ishikawa;H. Takagi;M. Nohara;N. Katayama;H. Sawa;M. Fujisawa;T. Kanai;J. Itatani;T. Mizokawa;Shik Shin;K. Okazaki
光致相变由于能够以超快的方式控制感兴趣的材料而得到了深入的研究，这可以诱导在平衡时无法获得的奇异相。然而，关键的机制仍在争论中，它一直是目前的一个中心问题，如何在光诱导相变过程中的电子，晶格和自旋自由度之间的耦合正在演变。在这里，我们开发了一种新的分析方法，频域角分辨光电子能谱，以获得精确的洞察电子-声子耦合在光诱导的绝缘体到金属的转变为Ta$_2$NiSe$_5$。我们证明了由位移激发产生的多个相干声子对电子具有带选择性耦合。此外，我们发现，晶格调制对应于2太赫兹声子模式，其中Ta晶格沿沿着a轴剪切，是最相关的光致半金属态。
Photo-induced phase transitions have been intensively studied owing to the ability to control a material of interest in the ultrafast manner, which can induce exotic phases unable to be attained at equilibrium. However, the key mechanisms are still under debate, and it has currently been a central issue how the couplings between the electron, lattice, and spin degrees of freedom are evolving during photo-induced phase transitions. Here, we develop a new analysis method, frequency-domain angle-resolved photoemission spectroscopy, to gain precise insight into electron-phonon couplings during photo-induced insulator-to-metal transitions for Ta$_2$NiSe$_5$. We demonstrate that multiple coherent phonons generated by displacive excitations show band-selective coupling to the electrons. Furthermore, we find that the lattice modulation corresponding to the 2 THz phonon mode, where Ta lattice is sheared along the a-axis, is the most relevant for the photo-induced semimetallic state.