1 Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800, China;2 School of Physical Science and Technology, ShanghaiTech University and Chinese Academy of Sciences-Shanghai Science Research Center, Shanghai 201210, China;3 Center for Excellence in Superconducting Electronics, State Key Laboratory of Functional Material for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, China;4 University of Chinese Academy of Sciences, Beijing 100049, China;5 Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA;6 Pohang Accelerator Laboratory, POSTECH, Pohang 790-784, Korea;7 Department of Physics, University of Oxford, Oxford, OX1 3PU, UK;8 National Laboratory of Solid State Microstructures, School of Physics and Department of Materials Science and Engineering, Nanjing University, Nanjing 210093, China;9 State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics and Collaborative Innovation Center of Quantum Matter, Tsinghua University, Beijing 100084, China>
Dirac semimetals are materials in which the conduction and the valence bands have robust crossing points protected by topology or symmetry. Recently, a new type of Dirac semimetals, so called the Dirac line-node semimetals (DLNSs), have attracted a lot of attention, as they host robust Dirac points along the one-dimensional (1D) lines in the Brillouin zone (BZ). In this work, using angle-resolved photoemission spectroscopy (ARPES) and first-principles calculations, we systematically investigated the electronic structures of non-symmorphic ZrSiS crystal where we clearly distinguished the surface states from the bulk states. The photon-energy-dependent measurements further prove the existence of Dirac line node along the X-R direction. Remarkably, by in situ surface potassium doping, we clearly observed the different evolutions of the bulk and surface electronic states while proving the robustness of the Dirac line node. Our studies not only reveal the complete electronic structures of ZrSiS, but also demonstrate the method manipulating the electronic structure of the compound.
Project supported by the National Key R&D Program of China (Grant No. 2017YFA0305400), Chinese Academy of Science——Shanghai Science Research Center (Grant No. CAS-SSRC-YH-2015-01), the National Natural Science Foundation of China (Grant No. 11674229), the Engineering and Physical Sciences Research Council Platform (Grant No. EP/M020517/1), and the Hefei Science——Center Chinese Academy of Sciences (Grant No. 2015HSC-UE013).