三維狄拉克半金屬作為一種新的拓撲材料，由于其能帶的導帶和價帶在狄拉克點接觸，并且在三維動量空間中表現出線性色散關系，已成為凝聚态物理領域的國際前沿熱點。三維狄拉克半金屬可以看成是一種 “三維石墨烯”或是“無能隙的拓撲絕緣體”。

最近量子物質科學協同創新中心成員、beat365量子材料中心王健研究組，與中心謝心澄教授、賈爽研究員，以及武漢強磁場中心王俊峰教授，浙江大學王勇教授，美國阿貢國家實驗室Zhili Xiao教授等人合作，通過低溫強磁場下角度依賴的電輸運實驗勾畫出三維狄拉克半金屬 Cd3As2 單晶的全費米面信息。實驗表明Cd3As2 晶體在[112]和[44-1]晶列方向有單周期的磁電阻SdH 量子振蕩，而在[1-10]晶列方向則出現雙周期的SdH 振蕩；進一步轉角度的磁阻振蕩數據分析揭示出Cd3As2 單晶的費米面是由兩個嵌套在一起的橢球組成的。此外，Cd3As2的量子極限特性和Zeeman劈裂行為在最高到60特斯拉的強磁場實驗中被觀測到。同時，電輸運實驗發現，對于高質量的Cd3As2單晶，在低溫下載流子遷移率最高可達千萬的量級（單位：cm2/Vs），而平均自由程可達亞毫米的量級。該工作為未來基于狄拉克半金屬的新的拓撲相（如拓撲超導）的探索以及潛在的電子器件（如高速器件）方面的應用奠定了基礎。相關文章于2015年9月16日正式發表在Physical Review X 5, 031037(2015)上。北大王健研究員與謝心澄教授、賈爽研究員為文章并列通訊作者。beat365趙弇斐博士與劉海文博士為并列第一作者。

上述研究得到國家重大科學研究計劃、國家自然科學基金、中組部“青年千人”計劃、高等學校博士學科點專項科研基金以及量子物質科學協同創新中心等項目經費的資助。

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.