Observation of Time-Reversal-Protected Single-Dirac-Cone Topological-Insulator States inBi2Te3andSb2Te3

Abstract

We show that the strongly spin-orbit coupled materials ${\mathrm{Bi}}_2{\mathrm{Te}}_3$ and ${\mathrm{Sb}}_2{\mathrm{Te}}_3$ and their derivatives belong to the $Z_2$ topological-insulator class. Using a combination of first-principles theoretical calculations and photoemission spectroscopy, we directly show that ${\mathrm{Bi}}_2{\mathrm{Te}}_3$ is a large spin-orbit-induced indirect bulk band gap ($\delta \sim 150\mathrm{meV}$) semiconductor whose surface is characterized by a single topological spin-Dirac cone. The electronic structure of self-doped ${\mathrm{Sb}}_2{\mathrm{Te}}_3$ exhibits similar $Z_2$ topological properties. We demonstrate that the dynamics of spin-Dirac fermions can be controlled through systematic Mn doping, making these materials classes potentially suitable for topological device applications.