Li Tao, Yao Da-Wei
Department of Physics, Renmin University of China, Beijing 100872, People's Republic of China.
J Phys Condens Matter. 2020 Mar 3;33(9):095601. doi: 10.1088/1361-648X/abce42.
The emergence of the coherent quasiparticle peak and the development of the peak-dip-hump structure in the anti-nodal region below T is the most prominent non-BCS signature of the under-doped high-T cuprates, in which no coherent quasiparticle can be defined in the anti-nodal region above T . The peak-dip-hump structure has been commonly interpreted as the result of the coupling of the electron to some Bosonic mode. However, such an electron-Boson coupling picture does not answer the question of why the quasiparticle dispersion is so flat in the anti-nodal region, a behavior totally unexpected for Bogoliubov quasiparticle in a d-wave BCS superconductor. Here we show that the sharp quasiparticle peak in the anti-nodal region should be understood as a new pole in the electron Green's function generated by the strong coupling of the electron to diffusive spin fluctuation around the antiferromagnetic wave vector Q = (π, π), rather than a nearly free Bogoliubov quasiparticle in a d-wave BCS superconductor. More specifically, we find that the normal self-energy of the electron from the scattering with the diffusive spin fluctuation manifests itself mainly as a level repulsion effect and is responsible for the reduction of both the quasiparticle dispersion and the quasiparticle dissipation rate in the anti-nodal region. We argue that the peak-dip separation in the anti-nodal spectrum should not be interpreted as the energy of the pairing glue.
低于转变温度(T)时，反节点区域中相干准粒子峰的出现以及峰-谷-峰结构的发展，是欠掺杂高温铜酸盐最显著的非BCS特征，其中在高于(T)的反节点区域中无法定义相干准粒子。峰-谷-峰结构通常被解释为电子与某种玻色子模式耦合的结果。然而，这种电子-玻色子耦合图景并不能回答为什么在反节点区域准粒子色散如此平坦的问题，这种行为对于d波BCS超导体中的博戈留波夫准粒子来说是完全出乎意料的。在这里，我们表明，反节点区域中尖锐的准粒子峰应被理解为由电子与反铁磁波矢(Q = (\pi, \pi))附近的扩散自旋涨落的强耦合所产生的电子格林函数中的一个新极点，而不是d波BCS超导体中近似自由的博戈留波夫准粒子。更具体地说，我们发现电子与扩散自旋涨落散射产生的正常自能主要表现为能级排斥效应，并导致反节点区域中准粒子色散和准粒子耗散率的降低。我们认为，反节点能谱中的峰-谷间距不应被解释为配对胶子的能量。
