Topological Aspect and Quantum Magnetoresistance of ${\hat{I}}^2$-Ag${}_2$Te

Abstract

To explain the unusual non-saturating linear magnetoresistance observed in silver chalcogenides, the quantum scenario has been proposed based on the assumption of gapless linear energy spectrum. Here we show, by first principles calculations, that ${\hat{I}}^2$-Ag${}_2$Te with distorted anti-fluorite structure is in fact a topological insulator with gapless Dirac-type surface states. The characteristic feature of this new binary topological insulator is the highly anisotropic Dirac cone, in contrast to known examples, such as Bi${}_2$Te${}_3$ and Bi${}_2$Se${}_3$. The Fermi velocity varies an order of magnitude by rotating the crystal axis.

4 pages, 4 figures