1State Key Laboratory of High Performance Computing, College of Computer, National University of Defense Technology, Changsha 410073 2Science and Technology on Surface Physics and Chemistry Laboratory, Jiangyou 621908 3National Innovation Institute of Defense Technology, Academy of Military Sciences PLA China, Beijing 100010 4Institute of Materials, China Academy of Engineering Physics, Mianyang 621700 5College of Advanced Interdisciplinary Studies, National University of Defense Technology, Changsha 410073 6Academy of Military Sciences PLA China, Beijing 100010 7Beijing Academy of Quantum Information Sciences, Beijing 100084
Abstract：Nodal line semimetal (NLS) is a new quantum state hosting one-dimensional closed loops formed by the crossing of two bands. The so-called type-II NLS means that these two crossing bands have the same sign in their slopes along the radial direction of the loop, which requires that the crossing bands are either right-tilted or left-tilted at the same time. According to the theoretical prediction, Mg$_{3}$Bi$_{2}$ is an ideal candidate for studying the type-II NLS by tuning its spin-orbit coupling (SOC). High-quality Mg$_{3}$Bi$_{2}$ films are grown by molecular beam epitaxy (MBE). By in-situ angle resolved photoemission spectroscopy (ARPES), a pair of surface resonance bands around the $\bar{{{\it \Gamma}}}$ point are clearly seen. This shows that Mg$_{3}$Bi$_{2}$ films grown by MBE are Mg(1)-terminated by comparing the ARPES spectra with the first principles calculations results. Moreover, the temperature dependent weak anti-localization effect in Mg$_{3}$Bi$_{2}$ films is observed under magneto-transport measurements, which shows clear two-dimensional (2D) $e$–$e$ scattering characteristics by fitting with the Hikami–Larkin–Nagaoka model. Therefore, by combining with ARPES, magneto-transport measurements and the first principles calculations, this work proves that Mg$_{3}$Bi$_{2}$ is a semimetal with topological surface states. This paves the way for Mg$_{3}$Bi$_{2}$ to be used as an ideal material platform to study the exotic features of type-II nodal line semimetals and the topological phase transition by tuning its SOC.
Xin J, Li G, Auffermann G, Borrmann H, Schnelle W, Gooth J, Zhao X, Zhu T, Felser C and Fu C 2018 Mater. Today Phys.7 61
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Chang C Z, Zhang J, Feng X, Shen J, Zhang Z, Guo M, Li K, Ou Y, Wei P, Wang L L, Ji Z Q, Feng Y, Ji S, Chen X, Jia J, Dai X, Fang Z, Zhang S C, He K, Wang Y, Lu L, Ma X C and Xue Q K 2013 Science340 167
2019, Vol. 36 
