Tunable ferromagnetic Weyl fermions from a hybrid nodal ring

Baobing Zheng,Jinzhu Zhao,Yujun Zhao,Rui Wang,Zhongjia Chen,Hu Xu,Bowen Xia

doi:10.1038/s41524-019-0214-z

Abstract

Realization of nontrivial band topology in condensed matter systems is of great interest in recent years. Using first-principles calculations and symmetry analysis, we propose an exotic topological phase with tunable ferromagnetic Weyl fermions in a half-metallic oxide CrP2O7. In the absence of spin–orbit coupling (SOC), we reveal that CrP2O7 possesses a hybrid nodal ring. When SOC is present, the spin-rotation symmetry is broken. As a result, the hybrid nodal ring shrinks to discrete nodal points and forms different types of Weyl points. The Fermi arcs projected on the (100) surface are clearly visible, which can contribute to the experimental study for the topological properties of CrP2O7. In addition, the calculated quasiparticle interference patterns are also highly desirable for the experimental study of CrP2O7. Our findings provide a good candidate of ferromagnetic Weyl semimetals, and are expected to realize related topological applications with their attracted features.

Highlights

Following the great advancements of topological insulators,[1,2] many efforts have been devoted to the studies of topological semimetals (TSMs) that present topologically nontrivial band structures
Contrary to fourfold-degenerate Dirac fermions, Weyl fermions, a concept derived from the high energy particle physics and realized in Weyl semimetal (WSM) systems,[18] are twofold degenerate at the crossing points (i.e., Weyl points) with breaking either time-reversal or inversion symmetries
WSMs that host unique Weyl fermions present nontrivial electronic structures, which leads to their topologically protected Fermi arc surface states, the negative magnetoresistance associated with the chiral anomaly, and anomalous Hall effect

Summary

INTRODUCTION

Following the great advancements of topological insulators,[1,2] many efforts have been devoted to the studies of topological semimetals (TSMs) that present topologically nontrivial band structures. In the case of a type-II Weyl cone, in contrast, tilting is severe enough that electron and hole pockets form.[10] WSMs that host unique Weyl fermions present nontrivial electronic structures, which leads to their topologically protected Fermi arc surface states, the negative magnetoresistance associated with the chiral anomaly, and anomalous Hall effect. These properties hold some potential applications for future electronic devices. The ferromagnetic phases with different magnetization associated with quasiparticle interference (QPI) pattern of CrP2O7. directions are almost degenerate, suggesting that the magnetiza-

AND DISCUSSION

Zheng et al 3

METHODS