Evidence for Two-dimensional Weyl Fermions in Air-Stable Monolayer PtTe$_{1.75}$

TL;DR

This paper reports the discovery of two-dimensional Weyl fermions in air-stable monolayer PtTe$_{1.75}$, characterized by advanced spectroscopy and calculations, revealing potential for novel spintronic device applications.

Contribution

It provides the first experimental realization of 2D Weyl fermions in monolayer PtTe$_{1.75}$ with strong spin-orbit coupling and stability in ambient conditions.

Findings

Identification of three pairs of Weyl cones in monolayer PtTe$_{1.75}$

Observation of giant Rashba splitting and band inversion

Monolayer PtTe$_{1.75}$ exhibits excellent air stability

Abstract

The Weyl semimetals represent a distinct category of topological materials wherein the low-energy excitations appear as the long-sought Weyl fermions. Exotic transport and optical properties are expected because of the chiral anomaly and linear energy-momentum dispersion. While three-dimensional Weyl semimetals have been successfully realized, the quest for their two-dimensional (2D) counterparts is ongoing. Here, we report the realization of 2D Weyl fermions in monolayer PtTe$_{1.75}$, which has strong spin-orbit coupling and lacks inversion symmetry, by combined angle-resolved photoemission spectroscopy, scanning tunneling microscopy, second harmonic generation, X-ray photoelectron spectroscopy measurements, and first-principles calculations. The giant Rashba splitting and band inversion lead to the emergence of three pairs of critical Weyl cones. Moreover, monolayer PtTe$_{1.75}$ exhibits excellent chemical stability in ambient conditions, which is critical for future device applications. The discovery of 2D Weyl fermions in monolayer PtTe$_{1.75}$ opens up new possibilities for designing and fabricating novel spintronic devices.