Crystalline Sb2Te3: Side Surfaces and Disappearance of Dirac Cones

Sb2Te3 is an end point of quasibinary GeTe-Sb2Te3 phase-change alloys and also a prototypical topological insulator (TI). TIs are materials that behave like insulators in their interior but whose surfaces are characterized by metallic states with linear dispersion, the so-called Dirac cones. Such surface states are symmetry protected, robust, and are maintained even in the presence of surface defects. It has been tacitly implied that any surfaces of a TI possess this property. Herein, using ab initio simulations, it is demonstrated that cleaving Sb2Te3 along certain side surfaces may lead to the disappearance of Dirac surface states. In particular, it is shown that the (110) surface of the typical TI Sb2Te3 is slightly gapped, whereas the (11 over bar 0) surface is metallic. The significance and potential benefits of the obtained results for practical applications in planar devices and memory cells are discussed.