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

## TL;DR

This paper predicts a Weyl semimetal phase in interfacial phase-change memory, explaining the giant conductivity difference between states through Weyl nodes and surface states, with implications for future memory devices.

## Contribution

It reveals the emergence of a Weyl semimetal phase in iPCM due to ferroelectric polarization, linking topological properties to conductivity switching.

## Key findings

- Weyl nodes cause giant conductivity enhancement in the SET state.
- Distinct surface states (Fermi arcs and closed Fermi surfaces) depend on termination.
- Weyl properties can be exploited for advanced memory device applications.

## Abstract

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.