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 (ARPES), we have observed such bulk Dirac cones in epitaxially-grown {\alpha}-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 (TI) phase. The nature of the Dirac cone crosses over from 3D to 2D as the film thickness is reduced.
@article{arxiv.1703.07488,
title = {Elemental topological Dirac semimetal: {\alpha}-Sn on InSb(111)},
author = {Cai-Zhi Xu and Yang-Hao Chan and Yige Chen and Peng Chen and Xiaoxiong Wang and Catherine Dejoie and Man-Hong Wong and Joseph Andrew Hlevyack and Hyejin Ryu and Hae-Young Kee and Nobumichi Tamura and Mei-Yin Chou and Zahid Hussain and Sung-Kwan Mo and Tai-Chang Chiang},
journal= {arXiv preprint arXiv:1703.07488},
year = {2017}
}