Elemental Topological Dirac Semimetal: <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>α</mml:mi></mml:math>-Sn on InSb(111)

Abstract

Three-dimensional (3D) topological Dirac semimetals (TDSs) are rare but\nimportant as a versatile platform for exploring exotic electronic properties\nand topological phase transitions. A quintessential feature of TDSs is 3D Dirac\nfermions associated with bulk electronic states near the Fermi level. Using\nangle-resolved photoemission spectroscopy (ARPES), we have observed such bulk\nDirac cones in epitaxially-grown {\\alpha}-Sn films on InSb(111), the first such\nTDS system realized in an elemental form. First-principles calculations confirm\nthat epitaxial strain is key to the formation of the TDS phase. A phase diagram\nis established that connects the 3D TDS phase through a singular point of a\nzero-gap semimetal phase to a topological insulator (TI) phase. The nature of\nthe Dirac cone crosses over from 3D to 2D as the film thickness is reduced.\n