Coexistence of Weyl semimetal and Weyl nodal loop semimetal phases in a collinear antiferromagnet

TL;DR

This paper predicts the coexistence of Weyl semimetal and Weyl nodal loop semimetal phases in the collinear antiferromagnet RuO2, offering a new material platform for experimental exploration of these topological states.

Contribution

The study theoretically demonstrates the coexistence and tunability of Weyl points and Weyl nodal loops in RuO2, a collinear antiferromagnet, which has not been experimentally verified before.

Findings

Weyl points and Weyl nodal loops coexist in RuO2

Weyl features can be tuned via Neel vector orientation

Weyl states are near the Fermi level, accessible by experiments

Abstract

Antiferromagnets (AFMs) with anomalous quantum responses have lead to new progress for the understanding of their magnetic and electronic structures from symmetry and topology points of view. Two typical topological states are the collinear antiferromagnetic Weyl semimetal (WSM) and Weyl nodal loop semimetal (WNLSM). In comparison with the counterparts in ferromagnets and non-collinear AFMs, the WSMs and WNLSMs in collinear AFMs are still waiting for experimental verification. In this work, we theoretically predicted the coexistence of Weyl points (WPs) and Weyl nodal loops (WNLs) in transition metal oxide RuO2. Owing to the small magnetocrystalline anisotropy energy, the WPs and WNLs can transform to each other via tuning the Neel vector. Moreover, since the WPs are very close to Fermi level and the WNLs are even crossing Fermi level, the topological states in RuO2 can be easily probed by photoemission and STM methods. Our result provides a promising material platform for the study of WSM and WNLSM states in collinear AFMs.