该研究团队报道了在铜氧化物超导体中普遍存在的两种共存电子模式耦合的发现。通过超高分辨率激光ARPES测量，研究人员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以上和以下的不同温度下，电子同时与两种尖锐模式（~70meV和~40meV）进行耦合。这些观测结果支持声子作为与电子耦合的模式的起源。而且，观察到的电子-模式耦合是不寻常的，因为相关的能量尺度在超导转变过程中没有表现出明显的能量漂移。
进一步的分析发现，以往被认为是超导标志的“峰-谷-驼峰”结构实际上是由更精细的“双峰-双谷-驼峰”结构组成，这些结构源于电子与两个尖锐模式的耦合。这些结果为理解~70-meV和~40-meV能量尺度及其随动量、掺杂和温度的演化提供了统一的图景，并为探索这些能量尺度在产生异常正常态和高温超导中的作用提供了关键信息。
据悉，在传统的超导体中，电子-声子耦合在超导性的产生过程中起着主导作用。然而，在高温铜氧化物超导体中，电子与声子以及其他玻色子模式的耦合及其对高温超导性的作用尚不清楚。虽然角分辨光电发射（ARPES）观测到了~70 meV的节点色散扭结和~40 meV的反节点色散扭结，被认为是电子-玻色子耦合的证据，但报道的结果并不一致，所涉及的玻色子的性质仍存在争议。
附：英文原文
Title: Ubiquitous coexisting electron-mode couplings in high-temperature cuprate superconductors
Author: 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.
Issue&Volume: 2023-10-18
Abstract: 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 ～70-meV nodal dispersion kink and ～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 ～70meV and ～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 ～70-meV and ～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 states and high-temperature superconductivity.
DOI: 10.1073/pnas.2219491120
Source: https://www.pnas.org/doi/abs/10.1073/pnas.2219491120