拓扑超导体FeSexTe1-x单晶超导性能与磁通钉扎  

Superconducting and flux pinning properties ofFeSexTe1-x topological superconductors

作　　者：梁超 张洁 赵可 羊新胜 赵勇 Liang Chao;Zhang Jie;Zhao Ke;Yang Xin-Sheng;Zhao Yong(School of Physical Science and Technology,Southwest Jiaotong University,Chengdu 610031,China;Superconductivity and New Energy R&D Center,Southwest Jiaotong University,Chengdu 610031,China)

机构地区：[1]西南交通大学物理科学与技术学院,成都610031 [2]西南交通大学超导与新能源研究开发中心,成都610031

出　　处：《物理学报》2020年第23期223-229,共7页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:51271155,51377138,51877180);国家重点研发计划(批准号:2017YFE0301402);国家高技术研究发展计划(批准号:2014AA032701);四川应用基础研究项目(批准号:2018JY0003)资助的课题.

摘　　要：铁基超导体FeSexTe1-x由于其具有上临界场高、各向异性小、临界电流密度大等优点,备受研究者的广泛关注.本文采用自助溶剂法生长得到了几种Se/Te组分比例不同的FeSexTe1-x单晶样品,对其结构和形貌进行了表征,并且对样品在低温下的磁性进行了测量.对样品超导态下临界电流密度、磁通钉扎力和磁场的关系进行了分析,讨论了样品在低温下的磁通钉扎模式.通过分析Se和Te的不同比例对上述性能的影响,确定了超导性能最佳的组分,为今后进一步研究FeSexTe1-x的超导与拓扑性质提供了参考.Iron-based superconductor FeSexTe1-x has attracted attention because of its high upper critical field,low anisotropy,and high critical current density.Also,it is predicted to have nontrivial topological properties,so that it is a candidate of realizing Majorana fermion,when the superconductivity is combined with topological features.However,its flux pinning behavior and mechanism in superconducting state with varying Se/Te ratio have not been systematically studied.We use self-flux method to grow single crystal samples of FeSexTe1-x with different x values(0.3,0.4,0.5 and 0.6).The structural and morphological properties of the monocrystalline samples are characterized by XRD and SEM.All samples show that they possess the expected crystalline structures and their lattice parameters vary with x value.The magnetic properties at low temperatures are also measured,showing that all samples have good superconductivity.Superconducting properties,such as critical current densities and flux pinning force densities,are extracted from the magnetic measurements and analyzed,and the flux pinning behavior is discussed.The best Se:Te ratio is determined to be nearly 0.4/0.6 based on the comparison among these properties of different samples.By utilizing the Dew-Hughes theory and analyzing the pinning force density peak,the flux pinning mechanism in the best samples(x=0.4,0.5)can be regarded as the mixture of normal point pinning and Dk volume pinning.This work provides important information for the further study of the topological and superconducting properties of FeSexTe1-x.

关 键 词：FeSexTe1-x 拓扑超导体 临界电流密度 磁通钉扎 

分 类 号：TM26[一般工业技术—材料科学与工程]