A novel quasi-one-dimensional topological insulator in bismuth iodide β-Bi4I4

• Published in: Nature materials Vol. 15; no. 2; pp. 154 - 158
• Main Authors: Autès, Gabriel, Isaeva, Anna, Moreschini, Luca, Johannsen, Jens C., Pisoni, Andrea, Mori, Ryo, Zhang, Wentao, Filatova, Taisia G., Kuznetsov, Alexey N., Forró, László, Van den Broek, Wouter, Kim, Yeongkwan, Kim, Keun Su, Lanzara, Alessandra, Denlinger, Jonathan D., Rotenberg, Eli, Bostwick, Aaron, Grioni, Marco, Yazyev, Oleg V.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.02.2016; Nature Publishing Group
• Subjects: 119/118; 121/135; 121/143; 140/125; 140/146; 639/766/119/2792; 639/766/119/544; 639/766/119/995; Biomaterials; Condensed Matter Physics; electronic properties and materials; letter; MATERIALS SCIENCE; Nanotechnology; Optical and Electronic Materials; surfaces, interfaces and thin films; topological matter
• ISSN: 1476-1122; 1476-4660
• DOI: 10.1038/nmat4488

The quasi-one-dimensional bismuth iodide β-Bi 4 I 4 is theoretically predicted and experimentally confirmed to exhibit a (1;110) Z 2 strong topological insulator phase. Recent progress in the field of topological states of matter 1 , 2 has largely been initiated by the discovery of bismuth and antimony chalcogenide bulk topological insulators (TIs; refs  3 , 4 , 5 , 6 ), followed by closely related ternary compounds 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 and predictions of several weak TIs (refs  17 , 18 , 19 ). However, both the conceptual richness of Z 2 classification of TIs as well as their structural and compositional diversity are far from being fully exploited. Here, a new Z 2 topological insulator is theoretically predicted and experimentally confirmed in the β-phase of quasi-one-dimensional bismuth iodide Bi 4 I 4 . The electronic structure of β-Bi 4 I 4 , characterized by Z 2 invariants (1;110), is in proximity of both the weak TI phase (0;001) and the trivial insulator phase (0;000). Our angle-resolved photoemission spectroscopy measurements performed on the (001) surface reveal a highly anisotropic band-crossing feature located at the  point of the surface Brillouin zone and showing no dispersion with the photon energy, thus being fully consistent with the theoretical prediction.