  The interfacial phase-change memory (iPCM) GeTe/Sb2Te3, promising candidates
for the next generation non-volatile random-access memories, exhibits
fascinating topological properties. Depending on the atomic-layer-stacking
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. But, its 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 produce 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 for future memory device applications.
