Interplay between altermagnetism and nonsymmorphic symmetries generating large anomalous Hall conductivity by semi-Dirac points induced anticrossings

TL;DR

This paper explores how altermagnetism and nonsymmorphic symmetries interact to produce large anomalous Hall conductivity through semi-Dirac points and anticrossings, with implications for magnetic topological phases.

Contribution

It reveals the role of nonsymmorphic symmetries and altermagnetism in generating complex band crossings and large anomalous Hall effects, including the influence of Neel vector orientation and spin-orbit coupling.

Findings

Altermagnetism appears only in C-type magnetic configurations.

Nonsymmorphic symmetries induce four-fold degeneracies with semi-Dirac dispersion.

Large anomalous Hall effect arises from SOC-induced band splitting and anticrossings.

Abstract

We investigate the interplay between altermagnetic spin-splitting and nonsymmorphic symmetries using the space group no. 62 as a testbed. Studying different magnetic orders by means of first-principles calculations, we find that the altermagnetism (AM) is present in the C-type magnetic configuration while it is absent for the G-type and A-type configurations due to different magnetic space group types. The nonsymmorphic symmetries constrain the system to a four-fold degeneracy at the border of the Brillouin zone with semi-Dirac dispersion. In the case of large hybridization as for transition metal pnictides, the interplay between AM and nonsymmorphic symmetries generates an intricate network of several crossings and anticrossings that we describe in terms of semi-Dirac points and glide symmetries. When we add the spin-orbit coupling (SOC), we find a Neel-vector dependent spin-orbit splitting at the time-reversal invariant momenta points since the magnetic space groups depend on the Neel vector. The magnetic space group type-I produces antiferromagnetic hourglass electrons that disappear in the type-III. When the Neel vector is along x, we observe a glide-protected crossing that could generate a nodal-line in the altermagnetic phase. The SOC splits the remaining band crossings and band anticrossings producing a large anomalous Hall effect in all directions excluding the Neel-vector direction