铁基122体系超导体的微结构与物性研究.docVIP

铁基122体系超导体的微结构与物性研 究 孙开徐程超张瑞心田焕芳李子安杨槐馨李建 中国科学院物理研究所 摘要： 铁基超导体的发现再次掀起了高温超导的研究热潮，由于铁基高温超导体具有 丰富的结构和物理性质，近十年来一直是科学界的重要研究领域之一.目前在多 个典型的铁基超导体系中已经证实，存在着结构相变和多重有序态之间的关联 与竞争.微结构研究和原位电子显微镜分析表明，典型122超导体系AFsAs? (A=Ca, Sr, Ba, Eu等)在低温区发生四方相到正交相结构相变，产生丰富的李 晶和微结构现象在CaFe2As2中存在织呢(tweed)结构，并在Ca原子层引起准 周期结构调制，平均周期为40 nm.在K,Fe2 xSe2超导体系中，存在丰富的相分离 现象 在a-b面内出现了复杂的畴结构.此外，A位元素的替代对AFe2As2体系母 相材料的结构特性和低温结构相变有重要影响，从而引起超导电性改变. 关键词： 铁基超导;结构类型;122体系;结构相变;相分离;物性; 作者简介：李建奇 E-mail: ljq@aphy.iphy.ac.cn 收稿日期：2017-06-03 基金：国家自然科学基金资助 Struetural phase transitions, phase separation and physical properties for the 122-system iron-based superconductors SUN Kai XU ChengChao ZHANG RuiXin TIAN HuanFang LI ZiAn YANG HuaiXin LI JianQi Institute of Physics, Chinese Academy of Sciences; Abstract： The discovery of iron-based supcrconductors stimulated the second research upsurge for high-temperature superconductors, which have been considered as one of the significant research field from both academic and technological points of view. It is noted that the studies of iron-based superconductors have brought a great development of a large number of experimcntai technologies and thcorctical researches in superconductivity physics. The remarkable correlations between structural transitions and multiple ordered states have been observed in the typical iron-based superconductors. According to the microstructure analyses and in-situ transmission electron microscopy (TEM) invcstigations, AFe2As2 (A=Ba, Sr and Ca) iron-based superconducting materials often show up a structural transition from tetragonal phase to orthorhombic phase from room temperature down to 20 K, resulting in visible twinning domains in the orthorhombic phase. The tetragonal SrFe2As2 samples, consistent with X-ray and neutron-diffraction data, undergo the tetragonalorthorhombic phase transition at about 205 K and show clear twin domains in the orthorhombic phase- On the other hand, T