铁基超导体隧道结的构筑和约瑟夫森效应研究  

Construction of tunnel junction and research on Josephson effect in iron-based superconductors

作　　者：王腾 于奥博 李春红 刘以鑫 彭炜 姜达 牟刚[1,3] WANG Teng;YU AoBo;LI ChunHong;LIU YiXin;PENG Wei;JIANG Da;MU Gang(National Key Laboratory of Materials for Integrated Circuits,Shanghai Institute of Microsystem and Information Technology,Chinese Academy of Sciences,Shanghai 200050,China;School of Physical Science and Technology,ShanghaiTech University,Shanghai 201210,China;University of Chinese Academy of Sciences,Beijing 100049,China;Beijing National Laboratory for Condensed Matter Physics,Institute of Physics,Chinese Academy of Sciences,Beijing 100190,China;Institute for Frontiers and Interdisciplinary Sciences,Zhejiang University of Technology,Hangzhou 310014,China)

机构地区：[1]中国科学院上海微系统与信息技术研究所,集成电路材料全国重点实验室,上海200050 [2]上海科技大学物质科学与技术学院,上海201210 [3]中国科学院大学,北京100049 [4]中国科学院物理研究所,北京凝聚态物理国家实验室,北京100190 [5]浙江工业大学前沿交叉科学研究院,杭州310014

出　　处：《中国科学：物理学、力学、天文学》2023年第12期201-209,共9页Scientia Sinica Physica,Mechanica & Astronomica

基　　金：中国科学院战略性先导专项(编号:XDB30000000);浙江工业大学人才计划启动基金(编号:202241637029)资助项目。

摘　　要：作为超导体中最重要的物理特性之一,约瑟夫森效应不但是超导电子学应用的基础,同时也在基础研究中有着重要的价值.本文针对铁基超导的两个体系:KCa_(2)Fe_(4)As_(4)F_(2)和FeSe_(0.5)Te_(0.5),开展了约瑟夫森效应研究.利用导电层-绝缘层-导电层交替堆叠的结构特点及其导致的强各向异性,对KCa_(2)Fe_(4)As_(4)F_(2)单晶c方向的电输运行为进行了探究.通过微纳加工等手段,成功降低了样品的尺寸和临界电流,从而大大减小了热效应对测量的影响,最终通过基于超导电子隧穿的A-B方程拟合临界电流随温度的变化行为获得了超导能隙方面的信息,并且观察到了临界电流随面内磁场周期性振荡的超导量子衍射行为,证明了该体系中本征约瑟夫森效应的存在.另外,利用机械剥离的方式制备了超薄FeSe_(0.5)Te_(0.5)单晶的约瑟夫森隧道结,并获得了其临界电流随温度和磁场的变化行为.分析表明,临界电流随温度的变化数据,同样可以被A-B方程很好地描述;从中提取出来的超导能隙值,与文献报道相一致.As one of the most significant physical characteristics of superconductors,the Josephson effect serves as the foundation of superconducting electronics applications and holds considerable value in fundamental research.In this work,we carried out investigations on the Josephson effect in two systems of iron-based superconductors:KCa_(2)Fe_(4)As_(4)F_(2) and FeSe_(0.5)Te_(0.5).We studied the intrinsic Josephson effect in KCa_(2)Fe_(4)As_(4)F_(2) single crystals based on the structural characteristics of alternating stacking of conductive and insulating layers and the resultant strong anisotropy.With micro/nano-fabrication,the sample size and critical current are successfully reduced,considerably decreasing the influence of the thermal effect on the measurements.Finally,information regarding the superconducting energy gap is obtained by fitting the temperature-dependent critical current behavior using the A-B equation based on superconducting electron tunneling.The behavior of superconducting quantum diffraction in terms of the periodic oscillation of critical current with the in-plane magnetic field is observed,confirming the existence of the intrinsic Josephson effect in this 12442 system.Additionally,a Josephson tunnel junction was prepared in ultrathin FeSe_(0.5)Te_(0.5) single crystals by mechanical exfoliation,and the evolution behavior of its critical current with temperature and magnetic field was obtained.The analysis shows that the A-B equation can accurately describe the temperature dependence of the critical current.Furthermore,the extracted superconducting energy gap value from the fitting is consistent with previous reports.

关 键 词：铁基超导 约瑟夫森效应 临界电流 超导能隙 

分 类 号：O469[理学—凝聚态物理]