Altermagnetic Weyl node-network semimetals protected by spin symmetry

TL;DR

This paper predicts new altermagnetic Weyl node-network semimetals protected by spin symmetry, expanding the understanding of topological phases and providing candidate materials for experimental investigation.

Contribution

It introduces a class of spin-symmetry protected Weyl nodal line semimetals and identifies specific materials, Nb2FeB2 and Ta2FeB2, as candidates with rich topological features.

Findings

Nb2FeB2 and Ta2FeB2 are predicted to be node-network semimetals.

Both materials have nodal rings protected by mirror symmetry.

Spin-orbit coupling induces a transition to Weyl semimetal phase.

Abstract

Symmetry protected topology has been studied extensively in the past twenty years, but the topology protected by spin symmetry has just begun to be studied. In this work, based on spin symmetry analysis, we propose that a class of Weyl nodal line semimetals is protected by the spin symmetry. Then, by the first-principles electronic structure calculations, we predict that both altermagnetic $\rm Nb_2FeB_2$ and $\rm Ta_2FeB_2$ are node-network semimetals protected by the spin symmetry. Moreover, both altermagnetic $\rm Nb_2FeB_2$ and $\rm Ta_2FeB_2$ have nodal rings protected by the mirror symmetry and Dirac points protected by nonsymmorphic spin symmetry. Furthermore, both altermagnetic $\rm Nb_2FeB_2$ and $\rm Ta_2FeB_2$ transform node-network semimetal phase into Weyl semimetal phase when considering spin-orbit coupling. Therefore, our work not only enriches the topological phases protected by spin symmetry, but also provides an excellent material platform to investigate the exotic physical properties of multiple altermagnetic topological semimetal phases in experiment.