反铁磁轴子绝缘体候选材料EuIn_(2)As_(2)的表面原子排布和电子结构  

Surface and electronic structure of antiferromagnetic axion insulator candidate EuIn_(2)As_(2)

作　　者：李渊 邓翰宾 王翠香 李帅帅 刘立民 朱长江 贾可 孙英开 杜鑫 于鑫 关童 武睿[1,3] 张书源 石友国 毛寒青[1] Li Yuan;Deng Han-Bin;Wang Cui-Xiang;Li Shuai-Shuai;Liu Li-Min;Zhu Chang-Jiang;Jia Ke;Sun Ying-Kai;Du Xin;Yu Xin;Guan Tong;Wu Rui;Zhang Shu-Yuan;Shi You-Guo;Mao Han-Qing(Beijing National Laboratory for Condensed Matter Physics,Institute of Physics,Chinese Academy of Sciences,Beijing 100190,China;School of Physics,University of Chinese Academy of Sciences,Beijing 100049,China;Songshan Lake Materials Laboratory,Dongguan 523808,China;Department of Physics,Cornell University,Ithaca 14853,USA;Center of Materials Science and Optoelectronics Engineering,University of Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]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 [2]中国科学院大学物理科学学院,北京100049 [3]松山湖材料实验室,东莞523808 [4]康奈尔大学物理系,伊萨卡14853 [5]中国科学院大学材料科学与光电技术学院,北京100049

出　　处：《物理学报》2021年第18期261-269,共9页Acta Physica Sinica

基　　金：国家重点研发计划(批准号:2016YFA0300602,2016YFA0302400,2017YFA0302903);国家自然科学基金(批准号:11227903);北京市科学技术委员会(批准号:Z181100004218007,Z191100007219011);国家重点基础研究发展计划(批准号:2015CB921304);中国科学院战略优先研究项目(批准号:XDB07000000,XDB28000000,XDB33000000)资助的课题.

摘　　要：非平庸的能带拓扑性与磁性结合可以产生丰富的量子现象,包括量子反常霍尔效应、轴子绝缘体态等.不同于磁性掺杂和异质结方案,内禀磁性拓扑绝缘体避免了掺杂带来的无序,且制备工艺通常比异质结更加简单,因此对研究和利用磁性拓扑绝缘体都有重要的意义.最近,EuIn_(2)As_(2)被认为是内禀反铁磁轴子绝缘体,本文使用低温扫描隧道显微镜研究了它的解理表面的原子排布和电子结构.结合原子分辨形貌图、晶格对称性分析以及局域态密度等信息,认为观测到的表面条纹结构来源于Eu截止面50%覆盖度的1×2表面重构.通过条纹面的局域态密度测量,发现4 K时费米能附近态密度存在非对称的谷-峰特征,该特征随温度升高逐渐变弱,在反铁磁相变温度以上完全消失,表明其与反铁磁序密切相关.此外,在某些台阶附近,伴随有少量迷宫状的结构,进一步分析认为可能是Eu原子形成的翘曲结构导致的.这些结果为理解EuIn_(2)As_(2)的表面能带结构和拓扑性质提供了重要信息.The interplay between non-trivial band topology and magnetic order can induce exotic quantum phenomena,such as the quantum anomalous Hall effect and axion insulator state.A prevalent approach to realizing such topological states is either by magnetic doping or through heterostructure engineering,while the former will bring in inhomogeneity and the latter requires complex procedures.Intrinsic magnetic topological insulators are expected to avoid the aforementioned disadvantages,which is of great significance in both studying and practically using these exotic quantum phenomena.Recently,a Zintl compound EuIn2As2 is predicted to be an intrinsic antiferromagnetic axion insulator.The bulk magnetic order of EuIn_(2)As_(2) has been reported in a lot of experiments,while the topological nature has not yet been confirmed.The surface properties of intrinsic magnetic topological insulators play an important role in the interplay between magnetic order and non-trivial surface state.Here in this work,we study the surface structure and electronic property of EuIn_(2)As_(2) single crystal by using scanning tunneling microscopy/spectroscopy(STM/S)and non-contact atomic force microscopy(NC-AFM).Considering the strength of bonds,the easy cleavage plane of the crystals possibly lies between In-In layers or between Eu-As layers.The STM topographies show that the cleaved surface is dominated by a striped pattern.And the dominated step height is an integer multiple of c/2,which implies that only one kind of cleavage plane is preferred.Atomic-resolved surface topographies show that the striped pattern is the 1×2 surface reconstruction with 50% coverage. Hence an In-terminated surface which will be 100% coverage is ruled out. The spatial evolution of STS near vacancies on the striped pattern shows a hole-doping feature. All of these results reveal that the striped pattern is the 1×2 surface reconstruction of the Eu terminated surface with 50% coverage. Using the STS, we measure the local densities of states on the striped surface at v

关 键 词：扫描隧道显微镜 EuIn_(2)As_(2) 磁性拓扑绝缘体 表面重构 

分 类 号：TB34[一般工业技术—材料科学与工程] O469[理学—凝聚态物理]