Hwang Jungseek
Department of Physics, Sungkyunkwan University, Suwon, Gyeonggi-do, 16419, Republic of Korea.
Sci Rep. 2021 Jun 3;11(1):11668. doi: 10.1038/s41598-021-91163-w.
Electron-boson spectral density functions (EBSDFs) can be obtained from measured spectra using various spectroscopic techniques, including optical spectroscopy. EBSDFs, known as glue functions, are suggested to have a magnetic origin. Here, we investigated EBSDFs obtained from the measured optical spectra of hole-doped cuprates with wide doping levels, from underdoped to overdoped cuprates. The average frequency of an EBSDF provides the timescale for the spin fluctuations to form Cooper pairs. This timescale is directly associated with retarded interactions between electrons. Using this timescale and Fermi velocity, a reasonable superconducting coherence length, which reflects the size of the Cooper pair, can be extracted. The obtained coherence lengths were consistent with those measured via other experimental techniques. Therefore, the formation of Cooper pairs in cuprates can be explained by spin fluctuations, the timescales of which appear in EBSDFs. Consequently, EBSDFs provide crucial information on the timescale of the microscopic mechanism of Cooper pair formation.
电子 - 玻色子谱密度函数（EBSDFs）可以通过使用包括光谱学在内的各种光谱技术从测量光谱中获得。EBSDFs，也就是所谓的胶合函数，被认为具有磁起源。在此，我们研究了从具有宽掺杂水平的空穴掺杂铜酸盐的测量光谱中获得的EBSDFs，这些铜酸盐涵盖了从欠掺杂到过掺杂的情况。EBSDF的平均频率为自旋涨落形成库珀对提供了时间尺度。这个时间尺度与电子之间的延迟相互作用直接相关。利用这个时间尺度和费米速度，可以提取出一个合理的超导相干长度，它反映了库珀对的大小。所获得的相干长度与通过其他实验技术测量的结果一致。因此，铜酸盐中库珀对的形成可以用自旋涨落来解释，其时间尺度出现在EBSDFs中。因此，EBSDFs提供了关于库珀对形成微观机制时间尺度的关键信息。
