Topological Insulating inGeTe/Sb2Te3Phase-Change Superlattice

Abstract

$\mathrm{GeTe}/{\mathrm{Sb}}_{2}{\mathrm{Te}}_{3}$ superlattice phase-change memory devices demonstrated greatly improved performance over that of ${\mathrm{Ge}}_{2}{\mathrm{Sb}}_{2}{\mathrm{Te}}_{5}$, a prototype record media for phase-change random access memory. In this work, we show that this type of $\mathrm{GeTe}/{\mathrm{Sb}}_{2}{\mathrm{Te}}_{3}$ superlattice exhibits topological insulating behavior on the basis of ab initio calculations. The analysis of the band structures and parities as well as ${Z}_{2}$ topological invariants unravels the topological insulating nature in these artificial materials. Furthermore, the topological insulating character remains in the $\mathrm{GeTe}/{\mathrm{Sb}}_{2}{\mathrm{Te}}_{3}$ superlattice under small compressive strains, whereas it is not observed as more ${\mathrm{Sb}}_{2}{\mathrm{Te}}_{3}$ building blocks introduced in the superlattice. The present results show that multifunctional data storages may be achieved in the $\mathrm{GeTe}/{\mathrm{Sb}}_{2}{\mathrm{Te}}_{3}$ superlattice. Such kinds of artificial materials can be used in phase-change random access memory, spintronics, and quantum computing.