Topological crystalline insulator in a new Bi semiconducting phase

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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 nM = −2, but not a Z2 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.
We acknowledge the computational support from the Extreme Science and Engineering Discovery Environment (XSEDE), which is supported by National Science Foundation Grant No. ACI-1053575. MGV and EVC acknowledge partial support from the Basque Country Government, Departamento de Educación, Universidades e Investigación (Grant No. IT-756-13), the Spanish Ministerio de Economía e Innovación (Grant No. FIS2010-19609-C02-01 and FIS2013-48286-C2-1-P), the FEDER funding, Saint Petersburg State University (Project No. 15.61.202.2015) and the Tomsk State University Competitiveness Improvement Program. FM thanks ‘Financiamiento Basal para Centros Cientificos y Tecnologicos de Excelencia FB 0807’ and Fondecyt grant 1150806. AHR acknowledge the support of DMREF-NSF 1434897 and the Donors of the American Chemical Society Petroleum Research Fund for partial support of this research under contract 54075-ND10. This work was supported by SPP 1666 of the Deutsche Forschungsgemeinschaft (DFG).