Elemental Topological Dirac Semimetal: α -Sn on InSb(111)

Author(s): Xu, CZ; Chan, YH; Chen, Y; Chen, P; Wang, X; Dejoie, C; Wong, MH; Hlevyack, JA; Ryu, H; Kee, HY; Tamura, N; Chou, MY; Hussain, Z; Mo, SK; Chiang, TC | Abstract: © 2017 American Physical Society. Three-dimensional (3D) topological Dirac semimetals (TDSs) are rare but important as a versatile platform for exploring exotic electronic properties and topological phase transitions. A quintessential feature of TDSs is 3D Dirac fermions associated with bulk electronic states near the Fermi level. Using angle-resolved photoemission spectroscopy, we have observed such bulk Dirac cones in epitaxially grown α-Sn films on InSb(111), the first such TDS system realized in an elemental form. First-principles calculations confirm that epitaxial strain is key to the formation of the TDS phase. A phase diagram is established that connects the 3D TDS phase through a singular point of a zero-gap semimetal phase to a topological insulator phase. The nature of the Dirac cone crosses over from 3D to 2D as the film thickness is reduced.