Band structure study of elemental topological material α-Sn on InSb(111)B

Research efforts on studying the band structure of elemental topological α-Sn have increased substantially in recent years. Bulk α-Sn is a zero-gap material with an inherent band inversion due to spin-orbit coupling. Interestingly, theoretical calculation proposed strained-induced topological phase transitions from topological Dirac semimetal (TDS) to topological insulator (TI) in α-Sn thin films. Among them, compressively strained α-Sn thin films on InSb(111)B were experimentally claimed to be a 3D TDS for 30-bilayer (BL) film by angle-resolved photoemission spectroscopy (ARPES).¹ In this work, α-Sn thin films were grown on InSb(111)B by molecular beam epitaxy (MBE) with epi-InSb as the starting surfaces prepared in the same MBE chamber. Single-crystal α-Sn thin films with excellent crystallinity and smooth surface morphology were characterized by X-ray diffraction and atomic force microscopy; their band structures were studied by ARPES. Much clearer band dispersions were observed for our 30-BL film compared to those in the literature, with virtually no k_z dependence over a wide photon energy range from 18 eV to 52 eV for the claimed 3D Dirac state. Our results, therefore, do not support the 3D TDS phase observed in the previous work.^1
1C. Z. Xu, et al., PRL 118, 146402 (2017).