强关联效应下非磁性元素Ir掺杂的SmFeAsO电子结构理论研究

基于密度泛函理论, 采用广义梯度近似方法 (SGGA+U) 计算分析了SmOFeAs电子结构以及 Ir 掺杂对该体系晶体结构和电子结构的影响. 结果表明, 随着Ir的掺杂, SmOFeAs晶体结构中FeAs层与SmO层之间的耦合增强, 晶体内部所含的铁砷四面体随着Ir掺杂其畸变性程度逐步减小. Fe3d以及As4p杂化轨道对体系电子结构起主要影响作用. Ir掺杂所引入的电子使FeAs层的巡游电子增多、Fe3d轨道中的 d_z2轨道离域性增强. 当Ir掺杂量为20%时, 费米面处于电子态密度峰值附近, 费米面急剧变化使该体系的T_c值有所增高, 反映了体系费米能级移动与其超导电性的密切关联性. 计算的电子态密度与XPS所得价带谱实验结果一致, 进一步验证了采用SGGA+U方法其包含修正d轨道局域电子的库仑势, 使得计算结果与实验结果更加接近. 关键词： U')" href="#">GGA+U SmOFeAs 晶体结构 电子结构

Study on the electronic structures of Iridium-doped SmOFeAs under the strongly correlated electrons effects

Based on the consideration of strong correlation of electrons, we have used density functional theory generalized gradient approximation method SGGA+U to calculate SmFeAsO and Ir doping effects on the lattices and electronic properties. It is found that iridium doping at the Fe site enhances the interaction between FeAs and SmO layers and results in a modification of the FeAs₄ tetrahedron. The electronic density of states (DOS) of SmOFe_1-xIr_xAs is studied by comparing the calculations with the X-ray photoemission spectroscopy experiments (XPS). It is revealed that the Fe 3d and As 4p hybridization orbits dominate the electric properties for SmOFe_1-xIr_xAs. Ir doping makes the five orbitals of Fe3d all filled. Superconductivity is sensitive to the peak position shifting away from Fermi level. Our VASP SGGA+U calculation provides a better agreement with the experimental results when we use an on-site coulomb energy of U on Fe 3d shell, which is sharply contrasted to the GGA process.
Keywords： U')" href="#">GGA+U SmOFeAs lattice electronic properties