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 ((Formula presented.)) surface is metallic. The significance and potential benefits of the obtained results for practical applications in planar devices and memory cells are discussed.