Kuz'min Valerii I, Nikolaev Sergey V, Korshunov Maxim M, Ovchinnikov Sergey G
Kirensky Institute of Physics, Federal Research Center KSC SB RAS, Akademgorodok, 660036 Krasnoyarsk, Russia.
Siberian Federal University, Svobodny Prospect 79, 660041 Krasnoyarsk, Russia.
Materials (Basel). 2023 Jun 27;16(13):4640. doi: 10.3390/ma16134640.
The physics of high-Tc superconducting cuprates is obscured by the effect of strong electronic correlations. One way to overcome this problem is to seek an exact solution at least within a small cluster and expand it to the whole crystal. Such an approach is at the heart of cluster perturbation theory (CPT). Here, we developed CPT for the dynamic spin and charge susceptibilities (spin-CPT and charge-CPT), with the correlation effects explicitly taken into account by the exact diagonalization. We applied spin-CPT and charge-CPT to the effective two-band Hubbard model for the cuprates obtained from the three-band Emery model and calculated one- and two-particle correlation functions, namely, a spectral function and spin and charge susceptibilities. The doping dependence of the spin susceptibility was studied within spin-CPT and CPT-RPA, that is, the CPT generalization of the random phase approximation (RPA). In the underdoped region, both our methods resulted in the signatures of the upper branch of the spin excitation dispersion with the lowest excitation energy at the (π,π) wave vector and no presence of low-energy incommensurate excitations. In the high doping region, both methods produced a low energy response at four incommensurate wave vectors in qualitative agreement with the results of the inelastic neutron scattering experiments on overdoped cuprates.
高温超导铜酸盐的物理性质因强电子关联效应而变得模糊不清。克服这一问题的一种方法是至少在一个小团簇内寻求精确解，并将其扩展到整个晶体。这种方法是团簇微扰理论（CPT）的核心。在此，我们开发了用于动态自旋和电荷磁化率的CPT（自旋-CPT和电荷-CPT），通过精确对角化明确考虑了关联效应。我们将自旋-CPT和电荷-CPT应用于从三带埃默里模型得到的铜酸盐的有效两带哈伯德模型，并计算了单粒子和双粒子关联函数，即谱函数以及自旋和电荷磁化率。在自旋-CPT和CPT-RPA（即随机相位近似（RPA）的CPT推广）中研究了自旋磁化率的掺杂依赖性。在欠掺杂区域，我们的两种方法都得出了自旋激发色散上支的特征，在（π,π）波矢处具有最低激发能，且不存在低能非 commensurate 激发。在高掺杂区域，两种方法在四个非 commensurate 波矢处都产生了低能响应，这与过掺杂铜酸盐的非弹性中子散射实验结果在定性上一致。
