Yan Hongtao, Bok Jin Mo, He Junfeng, Zhang Wentao, Gao Qiang, Luo Xiangyu, Cai Yongqing, Peng Yingying, Meng Jianqiao, Li Cong, Chen Hao, Song Chunyao, Yin Chaohui, Miao Taimin, Chen Yiwen, Gu Genda, Lin Chengtian, Zhang Fengfeng, Yang Feng, Zhang Shenjin, Peng Qinjun, Liu Guodong, Zhao Lin, Choi Han-Yong, Xu Zuyan, Zhou X J
National Lab for Superconductivity, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China.
Proc Natl Acad Sci U S A. 2023 Oct 24;120(43):e2219491120. doi: 10.1073/pnas.2219491120. Epub 2023 Oct 18.
In conventional superconductors, electron-phonon coupling plays a dominant role in generating superconductivity. In high-temperature cuprate superconductors, the existence of electron coupling with phonons and other boson modes and its role in producing high-temperature superconductivity remain unclear. The evidence of electron-boson coupling mainly comes from angle-resolved photoemission (ARPES) observations of [Formula: see text]70-meV nodal dispersion kink and [Formula: see text]40-meV antinodal kink. However, the reported results are sporadic and the nature of the involved bosons is still under debate. Here we report findings of ubiquitous two coexisting electron-mode couplings in cuprate superconductors. By taking ultrahigh-resolution laser-based ARPES measurements, we found that the electrons are coupled simultaneously with two sharp modes at [Formula: see text]70meV and [Formula: see text]40meV in different superconductors with different dopings, over the entire momentum space and at different temperatures above and below the superconducting transition temperature. These observations favor phonons as the origin of the modes coupled with electrons and the observed electron-mode couplings are unusual because the associated energy scales do not exhibit an obvious energy shift across the superconducting transition. We further find that the well-known "peak-dip-hump" structure, which has long been considered a hallmark of superconductivity, is also omnipresent and consists of "peak-double dip-double hump" finer structures that originate from electron coupling with two sharp modes. These results provide a unified picture for the [Formula: see text]70-meV and [Formula: see text]40-meV energy scales and their evolutions with momentum, doping and temperature. They provide key information to understand the origin of these energy scales and their role in generating anomalous normal state and high-temperature superconductivity.
在传统超导体中，电子 - 声子耦合在产生超导性方面起主导作用。在高温铜酸盐超导体中，电子与声子及其他玻色子模式的耦合的存在及其在产生高温超导性中的作用仍不明确。电子 - 玻色子耦合的证据主要来自对70毫电子伏特节点色散扭结和40毫电子伏特反节点扭结的角分辨光电子能谱（ARPES）观测。然而，报道的结果是零散的，所涉及玻色子的性质仍在争论中。在此，我们报告了在铜酸盐超导体中普遍存在的两种共存电子模式耦合的发现。通过进行基于超高分辨率激光的ARPES测量，我们发现在不同掺杂的不同超导体中，在整个动量空间以及超导转变温度上下的不同温度下，电子同时与70毫电子伏特和40毫电子伏特的两个尖锐模式耦合。这些观测结果支持声子作为与电子耦合的模式的起源，并且所观测到的电子 - 模式耦合是不寻常的，因为相关的能量尺度在超导转变时没有表现出明显的能量偏移。我们进一步发现，长期以来被认为是超导性标志的著名的“峰 - 谷 - 峰”结构也是普遍存在的，并且由源自电子与两个尖锐模式耦合的“峰 - 双峰 - 双驼峰”更精细结构组成。这些结果为70毫电子伏特和40毫电子伏特的能量尺度及其随动量、掺杂和温度的演变提供了一个统一的图景。它们为理解这些能量尺度的起源及其在产生反常正常态和高温超导性中的作用提供了关键信息。
