A new class of large band gap quantum spin hall insulators: 2D fluorinated group-IV binary compounds

• Published in: Scientific reports Vol. 6; no. 1; p. 26123
• Main Authors: Padilha, J. E., Pontes, R. B., Schmidt, T. M., Miwa, R. H., Fazzio, A.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 23.05.2016; Nature Publishing Group
• Subjects: 639/301/357/1018; 639/766/119/2792; 639/925/357/995; Band gap; Conduction; Humanities and Social Sciences; multidisciplinary; Science
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/srep26123

We predict a new class of large band gap quantum spin Hall insulators, the fluorinated PbX (X = C, Si, Ge and Sn) compounds, that are mechanically stable two-dimensional materials. Based on first principles calculations we find that, while the PbX systems are not topological insulators, all fluorinated PbX (PbXF 2 ) compounds are 2D topological insulators. The quantum spin Hall insulating phase was confirmed by the explicitly calculation of the Z 2 invariant. In addition we performed a thorough investigation of the role played by the (i) fluorine saturation, (ii) crystal field and (iii) spin-orbital coupling in PbXF 2 . By considering nanoribbon structures, we verify the appearance of a pair of topologically protected Dirac-like edge states connecting the conduction and valence bands. The insulating phase which is a result of the spin orbit interaction, reveals that this new class of two dimensional materials present exceptional nontrivial band gaps, reaching values up to 0.99 eV at the Γ point and an indirect band gap of 0.77 eV. The topological phase is arisen without any external field, making this system promising for nanoscale applications, using topological properties.