三维狄拉克半金属作为一种新的拓扑材料，由于其能带的导带和价带在狄拉克点接触，并且在三维动量空间中表现出线性色散关系，已成为凝聚态物理领域的国际前沿热点。三维狄拉克半金属可以看成是一种 “三维石墨烯”或是“无能隙的拓扑绝缘体”。

最近量子物质科学协同创新中心成员、北京大学量子材料中心王健研究组，与中心谢心澄教授、贾爽研究员，以及武汉强磁场中心王俊峰教授，浙江大学王勇教授，美国阿贡国家实验室Zhili Xiao教授等人合作，通过低温强磁场下角度依赖的电输运实验勾画出三维狄拉克半金属 Cd3As2 单晶的全费米面信息。实验表明Cd3As2 晶体在[112]和[44-1]晶列方向有单周期的磁电阻SdH 量子振荡，而在[1-10]晶列方向则出现双周期的SdH 振荡；进一步转角度的磁阻振荡数据分析揭示出Cd3As2 单晶的费米面是由两个嵌套在一起的椭球组成的。此外，Cd3As2的量子极限特性和Zeeman劈裂行为在最高到60特斯拉的强磁场实验中被观测到。同时，电输运实验发现，对于高质量的Cd3As2单晶，在低温下载流子迁移率最高可达千万的量级（单位：cm2/Vs），而平均自由程可达亚毫米的量级。该工作为未来基于狄拉克半金属的新的拓扑相（如拓扑超导）的探索以及潜在的电子器件（如高速器件）方面的应用奠定了基础。相关文章于2015年9月16日正式发表在Physical Review X 5, 031037(2015)上。北大王健研究员与谢心澄教授、贾爽研究员为文章并列通讯作者。北京大学赵弇斐博士与刘海文博士为并列第一作者。

上述研究得到国家重大科学研究计划、国家自然科学基金、中组部“青年千人”计划、高等学校博士学科点专项科研基金以及量子物质科学协同创新中心等项目经费的资助。

An article in Physical Review X reporting Anisotropic Fermi Surface and Quantum Limit Transport in High Mobility Three-Dimensional Dirac Semimetal Cd3As2

The three-dimensional topological Dirac semimetal, as a new type of topological materials, has attracted great attention in condensed matter physics. There, the conduction and valence band touch only at discrete points and disperse linearly along all (three) momentum directions—a natural 3D counterpart of graphene, as well as a gapless topological insulator.

Prof. Jian Wang at PKU, in collaboration with Prof. Xincheng Xie at PKU (theory), Prof. Shuang Jia at PKU (single crystal sample growth), Prof. Junfeng Wang at WNHMFC (Pulsed high magnetic field measurement), Prof. Yong Wang at ZJU (TEM measurements), as well as Prof. Zhili Xiao at the Argonne National Laboratory (single crystal XRD measurement) made new achievement in the magnetotransport in Cd3As2 single crystal to show the complete three dimensional Fermi surface. From the SdH analysis in different magnetic field direction, it is found when the magnetic field lies in [112] and [44-1] axis, only single oscillation period features present, however, the system shows double period oscillations when the field is applied along [1-10] direction. Moreover, combined with angular dependence of SdH oscillations at different magnetic field directions, they illustrate a complete 3D Fermi surfaces with two nested anisotropic ellipsoids around the Dirac points. Furthermore, by measuring the magnetoresistance up to 60 T, the quantum limit (n = 1 Landau level) at about 43 T is observed. In addition, ultrahigh mobility up to the scale of 10 million cm2/Vs is detected. The results were published in Physical Review X (PRX 5, 031037(2015)). Jian Wang, X.C. Xie and Shuang Jia at PKU are corresponding authors of this paper. Yanfei Zhao and Haiwen Liu at PKU contributed equally to this work.

The work was supported by National Basic Research Programs of China, National Natural Science Foundation of China, 1000 Talents Program for Young Scientists of China, the Research Fund for the Doctoral Program of Higher Education (RFDP) of China, and Collaborative Innovation Center of Quantum Matter, China.