Weyl node assisted conductivity switch in interfacial phase-change memory with van der Waals interfaces

Abstract

The interfacial phase-change memory (iPCM) GeTe/Sb2Te3, a promising candidate for the next generation nonvolatile random-accessmemories, exhibits fascinating topological properties. Depending on the atomic-layerstacking sequence of the GeTe block, the iPCM can be either in the SET (Ge-Te-Ge-Te) or RESET (Te-Ge-Ge-Te) states, where the former exhibits ferroelectric polarization and electrical conductivity two orders of magnitude larger than that of the RESET state. Yet, its microscopic origin remains elusive. Here, we predict the emergence of a Weyl semimetal phase in the SET state induced by the ferroelectric polarization which breaks the crystal inversion symmetry. We show that the giant conductivity enhancement of the SET phase is due to the appearance of gapless Weyl nodes. The Ge-Te-or Sb-Te-terminated surfaces of Weyl semimetal iPCM exhibit surface states with completely distinctive topology, where the former consists solely of Fermi arcs while the latter consists of both closed Fermi surface and open Fermi arcs. The iPCM with van der Waals interfaces offers an ideal platform for exploiting the exotic Weyl properties as well as for future memory device applications.