# An ideal Weyl semimetal induced by magnetic exchange

## TL;DR

This paper proposes EuCd$_2$As$_2$ as a magnetic Weyl semimetal with a single pair of Weyl nodes induced by magnetic exchange, confirmed through multiple experimental and theoretical methods, enabling new tests of Weyl physics.

## Contribution

It introduces EuCd$_2$As$_2$ as a magnetic Weyl semimetal with a controllable Weyl node pair, advancing material realization for Weyl physics studies.

## Key findings

- Weyl nodes are induced by magnetic exchange in EuCd$_2$As$_2$
- Weyl nodes are near the Fermi level and isolated from other bands
- Experimental evidence from ARPES, quantum oscillations, and Hall measurements

## Abstract

Weyl semimetals exhibit exceptional quantum electronic transport due to the presence of topologically-protected band crossings called Weyl nodes. The nodes come in pairs with opposite chirality, but their number and location in momentum space is otherwise material specific. Following the initial discoveries there is now a need for better material realizations, ideally comprising a single pair of Weyl nodes located at or very close to the Fermi level and in an energy window free from other overlapping bands. Here we propose the layered intermetallic EuCd$_2$As$_2$ to be such a system. We show that Weyl nodes in EuCd$_2$As$_2$ are magnetically-induced via exchange coupling, emerging when the Eu spins are aligned by a small external magnetic field. The identification of EuCd$_2$As$_2$ as a model magnetic Weyl semimetal, evidenced here by ab initio calculations, photoemission spectroscopy, quantum oscillations and anomalous Hall transport measurements, opens the door to fundamental tests of Weyl physics.