Elemental topological Dirac semimetal: {\alpha}-Sn on InSb(111)

TL;DR

This paper reports the discovery of a topological Dirac semimetal phase in epitaxial {\

Contribution

It demonstrates the realization of a 3D topological Dirac semimetal in elemental {\

Findings

Observation of bulk Dirac cones in {\

Confirmation that epitaxial strain induces the TDS phase

Abstract

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.