Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025, USA.
Science. 2014 Feb 21;343(6173):864-7. doi: 10.1126/science.1245085. Epub 2014 Jan 16.
Three-dimensional (3D) topological Dirac semimetals (TDSs) represent an unusual state of quantum matter that can be viewed as "3D graphene." In contrast to 2D Dirac fermions in graphene or on the surface of 3D topological insulators, TDSs possess 3D Dirac fermions in the bulk. By investigating the electronic structure of Na3Bi with angle-resolved photoemission spectroscopy, we detected 3D Dirac fermions with linear dispersions along all momentum directions. Furthermore, we demonstrated the robustness of 3D Dirac fermions in Na3Bi against in situ surface doping. Our results establish Na3Bi as a model system for 3D TDSs, which can serve as an ideal platform for the systematic study of quantum phase transitions between rich topological quantum states.
三维（3D）拓扑狄拉克半金属（TDS）代表了一种特殊的量子物质状态，可以被视为“3D 石墨烯”。与石墨烯或 3D 拓扑绝缘体表面的二维狄拉克费米子不同，TDS 在体相中具有 3D 狄拉克费米子。通过角分辨光电子能谱研究 Na3Bi 的电子结构，我们探测到了在所有动量方向上具有线性色散的 3D 狄拉克费米子。此外，我们还证明了 Na3Bi 中的 3D 狄拉克费米子对原位表面掺杂的稳定性。我们的结果确立了 Na3Bi 作为 3D TDS 的模型体系，它可以作为系统研究丰富拓扑量子态之间量子相变的理想平台。
