%A Tong Zhou, Xie-Gang Zhu, Mingyu Tong, Yun Zhang, Xue-Bing Luo, Xiangnan Xie, Wei Feng, Qiuyun Chen, Shiyong Tan, Zhen-Yu Wang, Tian Jiang, Yuhua Tang, Xin-Chun Lai, Xuejun Yang %T Experimental Evidence of Topological Surface States in Mg$_{3}$Bi$_{2}$ Films Grown by Molecular Beam Epitaxy %0 Journal Article %D 2019 %J Chin. Phys. Lett. %R 10.1088/0256-307X/36/11/117303 %P 117303%V 36 %N 11 %U {https://cpl.iphy.ac.cn/CN/abstract/article_105456.shtml} %8 2019-10-15 %X 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.