1 MoSi 2 N 4 : An emerging 2D electronic material with protected band edge states and dielectric tunable quasiparticle and optical properties Yabei Wu, 1,2,3,‡ Zhao Tang, 4,‡ Weiyi Xia, 4 Weiwei Gao, 5 Fanhao Jia, 4,6 Yubo Zhang, 1,2 Wenguang Zhu, 3 Wenqing Zhang, 1,2,† and Peihong Zhang 4, † 1. Department of Physics and Shenzhen Institute for Quantum Science & engineering, Southern University of Science and Technology, Shenzhen, Guangdong 518055, China 2. Guangdong Provincial Key Lab for Computational Science and Materials Design, and Shenzhen Municipal Key Lab for Advanced Quantum Materials and Devices, Southern University of Science and Technology, Shenzhen, Guangdong 518055, China 3. ICQD, Hefei National Laboratory for Physical Science at the Microscale, Key Laboratory of Strongly-Coupled Quantum Matter Physics, Chinese Academy of Sciences, Department of Physics, and Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China 4. Department of Physics, University at Buffalo, State University of New York, Buffalo, New York 14260, USA 5. Department of Physics, Dalian University of Technology, Dalian, Liaoning 116024, China 6. International Centre for Quantum and Molecular Structures, Materials Genome Institute, Department of Physics, Shanghai University, 99 Shangda Road, Shanghai 200444 China † zhangwq@sustech.edu.cn; pzhang3@buffalo.edu ‡ These authors contributed equally to this work.