Topological Crystalline Insulator in a New Bi Semiconducting Phase

• Published in: Scientific reports 2016-02, Vol.6 (1), p.21790-21790, Article 21790
• Main Authors: Munoz, F., Vergniory, M. G., Rauch, T., Henk, J., Chulkov, E. V., Mertig, I., Botti, S., Marques, M. A. L., Romero, A. H.
• Format: Article
• Language: English
• Subjects: 639/301/119/2792; 639/766/94; Chemical Sciences; Delinquency; Engineering Sciences; Humanities and Social Sciences; multidisciplinary; Phase transitions; Physics; Science; Symmetry
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/srep21790

Topological crystalline insulators are a type of topological insulators whose topological surface states are protected by a crystal symmetry, thus the surface gap can be tuned by applying strain or an electric field. In this paper we predict by means of ab initio calculations a new phase of Bi which is a topological crystalline insulator characterized by a mirror Chern number n M  = −2, but not a strong topological insulator. This system presents an exceptional property: at the (001) surface its Dirac cones are pinned at the surface high-symmetry points. As a consequence they are also protected by time-reversal symmetry and can survive against weak disorder even if in-plane mirror symmetry is broken at the surface. Taking advantage of this dual protection, we present a strategy to tune the band-gap based on a topological phase transition unique to this system. Since the spin-texture of these topological surface states reduces the back-scattering in carrier transport, this effective band-engineering is expected to be suitable for electronic and optoelectronic devices with reduced dissipation.