Munoz, F., Garcia Vergniory, M., Rauch, T., Henk, J., Chulkov, E. V., Mertig, I., Botti, S., Marques, M. A. L., Romero Castro, A. H.

Topological crystalline insulator in a new Bi semiconducting phase
Scientific Reports **6**, (21),pp 21790/1-9 (2016)
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 Z_{2} 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.

TH-2016-08