Experimental Realization of a Quaternary Bi-Chalcogenide Topological Insulator with Smaller Effective Mass

• Published in: Journal of physical chemistry. C Vol. 123; no. 23; pp. 14398 - 14403
• Main Authors: Goncalves, Pedro H. R, Calil, Luan, Antoniazzi, Igor, Chagas, Thais, Malachias, Ângelo, Soares, Edmar A, de Carvalho, Vagner E, Miquita, Douglas R, Magalhães-Paniago, Rogério, Silva, Wendell S
• Format: Journal Article
• Language: English
• Published: American Chemical Society 13.06.2019
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/acs.jpcc.9b01811

It is known that Sb2Se3 does not exhibit topological insulator behavior due to its orthorhombic structure. The introduction of a small amount of bismuth and tellurium may change its structure to hexagonal, leading to a stable topological insulator compound. We report here the synthesis and the structural, chemical, and electronic properties of the topological insulator BiSbSe2.5Te0.5. Combining X-ray and electron diffraction measurements, we demonstrate the formation of this stable quaternary hexagonal single crystal. We used X-ray photoelectron spectroscopy to determine quantitatively the exact chemical composition of the sample. The topological insulating behavior is similar to that of other bismuth chalcogenides, as probed by angle-resolved photoemission spectroscopy. A p-type doping, leading to a 0.15 eV shift of the Fermi level was found. This value compensates the intrinsically n-type doping produced by selenium vacancies. We also found a smaller effective mass and a higher electron group velocity for the electrons in the topological states compared with Bi2Se3.