新型交生结构自掺杂铁基超导体  

Self-doped iron-based superconductors with intergrowth structures

作　　者：王志成 曹光旱 Wang Zhi-Cheng;Cao Guang-Han(State Key Laboratory of Silicon Materials,Department of Physics,Zhejiang University,Hangzhou 310027,China;Collaborative Innovation Centre of Advanced Microstructures,Nanding 210093,China)

机构地区：[1]浙江大学物理学系硅材料国家重点实验室,杭州310027 [2]南京大学人工微结构科学与技术协同创新中心,南京210093

出　　处：《物理学报》2018年第20期142-157,共16页Acta Physica Sinica

基　　金：国家自然科学基金重大项目(批准号:11190023);国家重点基础研究发展计划(批准号:2016YFA0300202,2017YFA0303002);中央高校基本科研业务费专项资金资助的课题

摘　　要：铁基高温超导体的基本结构单元是反萤石型Fe_2X_2层(X为磷族或硫族元素),因此,设计具有Fe_2X_2层的新化合物成为探索铁基超导材料的有效途径.本文在回顾铁基超导体结构特征和基本结构类型的基础上,归纳总结了铁基超导体块层结构设计的基本原则;着重介绍迄今发现的几类具有层状交生(intergrowth)结构的新型自掺杂铁基超导材料.The key structural unit of iron-based superconductors（FeSCs） is the Fe2 X2（ ＂X＂ refers to a pnictogen or a chalcogen element） layer which stacks alternately along the crystallographic c axis with other spacer layers. This structural feature makes it possible to find FeSCs via rational material design. In this paper, we first review the crystal structure of FeSCs along with the relevant progress. Then we summarize several rules for designing the intergrowth structures. The rules include the following points. 1） Lattice match between the intergrowth layers should be good enough. Quantitatively,the lattice mismatch, defined as μ=2（aA-aB）/（aA＋aB）,where aA and aB are respectively the lattice parameters of the two constituent compounds, should be no larger than ～2%. 2） The charge transfer between the intergrowth layers is mostly essential, which acts as the glue that combines the constituent layers together. Such a charge transfer also induces the extra charge carriers in the superconducting key layer to give rise to superconductivity without extrinsic doping（so-called ＂self doping＂）. 3） For the structure with similar yet crystallographically distinct sites, one needs to avoid forming solid solutions. 4） Each intergrowth layer is preferably thermodynamically stable. 5） The designed structure can be preliminary evaluated with the ＂hard and soft acids and bases＂ conception and ab initio calculations.Following these empirical rules, we introduce and analyze five examples,namely,（Li（0.8）Fe（0.2）OH）FeSe,Ba2 Ti2 Fe4 As4 O,42214-type Ln4 Fe2 As2 Te（1-x）O4（Ln = Pr, Sm, Gd）, 1144-type AkAeFe4 As4（Ak = K, Rb, Cs; Ae = Ca,Sr,Eu）,and 12442-type AkCa2 Fe4 As4 F2 and AkLn2 Fe4 As4 O2（Ak = K,Rb, Cs; Ln = Nd-Ho）. For the last 12442-type compounds, we also discuss the unusual relation between superconducting transition temperature and crystallographic parameters. We conclude that the structural-design approach may serve as an effective route, not only for discove

关 键 词：铁基超导体 结构设计 自掺杂 

分 类 号：O511.3[一般工业技术—材料科学与工程]