强关联效应下非磁性元素Ir掺杂的SmFeAsO电子结构理论研究  

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

作　　者：潘敏[1] 黄整[1] 赵勇[1,2] 

机构地区：[1]超导与新能源研究开发中心,材料先进技术教育部重点实验室,西南交通大学,四川610031 [2]澳大利亚新南威尔士大学,材料科学与工程学院

出　　处：《物理学报》2013年第21期338-343,共6页Acta Physica Sinica

基　　金：国家磁约束核聚变能研究专项项目(批准号:2011GB112001);国际合作项目(批准号:2013DFA51050);中央高校基本科研业务费资助项目(批准号:SWJTU12CX019;2682013ZT16;SWJTU11ZT31;2682013CX004);国家自然科学基金(批准号:51271155)资助的课题~~

摘　　要：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dz2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Tc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.Based on the consideration of strong correlation of electrons, we have used density functional theory generalized gradient ap- proximation 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 SmOFel_xIrxAs is studied by comparing the calculations with the X-ray photoe- mission spectroscopy experiments （XPS）. It is revealed that the Fe 3d and As 4p hybridization orbits dominate the electric properties for SmOFex_xIrxAs. 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.

关 键 词：GGA+U SmOFeAs 晶体结构 电子结构 

分 类 号：O469[理学—凝聚态物理]