PtNiO2: A magnetic Weyl semimetal with large anomalous Hall conductivity

Abstract

Magnetic Weyl semimetals represent a new class of topological systems housing Weyl fermions as emergent quasiparticles. These materials exhibit exotic electronic transport phenomena, such as the anomalous Hall conductivity (AHC) driven by the intrinsic Berry curvature arising from Weyl fermions. Here, we investigate the structural, electronic, magnetic, and topological properties of delafossite PtNiO2 by means of the density functional theory approach. The titled compound is found to be structurally stable with a ferromagnetic ground state. The electronic structure calculation indicates a half-metallic feature with an effective magnetic moment of 1 μB per unit cell. Triple degenerate points (TDPs) are noted in the electronic band structure that arises from the touching of nodal lines and a single band. These TDPs split to distinct Weyl points when spin–orbit coupling is taken into account, shedding light on the topological properties of the material. A total of 12 (24) Weyl points were found within 100 meV below and above the Fermi level (EF) along the magnetic easy [100] (hard [001]) axis. The intrinsic AHC is found prominent at and around EF, and in particular, where the number of Weyl points is located. The calculated AHC value along the easy axis is ∼185 Ω−1 cm−1 within 20 meV below EF, while along the hard-axis, the value rises from ∼600 Ω−1 cm−1 at EF to 765 Ω−1 cm−1 within 30 meV. These values are comparable to those observed in other well-known Weyl semimetals. Our finding is expected to motivate the experimentalist in exploring the topological properties of delafossite materials.