Anomalous transport in itinerant van der Waals ferromagnets Fe${}_n$GeTe${}_2$ (\emph{n}=3, 4, 5)

Abstract

Ferromagnetic (FM) semimetals Fe${}_n$GeTe${}_2$(n=3, 4, 5), exhibit several symmetry-protected band-crossing points or lines near the Fermi energy (E${}_F$) and these topological properties of energy bands lead to interesting transport properties. We study these materials employing the first-principle calculations and the tight-binding Hamiltonian constructed by fitting the parameters of the first principles calculation. In the presence of spin-orbit coupling (SOC) for n=3,5 a large Berry curvature (BC) concentrated on the nodal lines is observed. The consequence of the correlation of the topological nodal line and magnetic moments on anomalous Hall conductivity (AHC) $\ddot{I}{ƒ}_{xy}$ and anomalous Nernst conductivity (ANC) $\hat{I}{\pm }_{xy}$ have been investigated. We find $\ddot{I}{ƒ}_{xy}=150$ S/cm for n=3, 295 S/cm for n=4, and 90 S/cm for n=5 at 0 K, while the ANC is observed as $\hat{I}{\pm }_{xy}=0.55$ A/Km for n=3, 0.10 A/Km for n=5, and 0.80 A/Km for n=4, at the E${}_F$ at room temperature. Our calculated AHC values at 0 K, i.e., 150 S/cm for Fe${}_3$GeTe${}_2$ and 90 S/cm Fe${}_5$GeTe${}_2$, are consistent with the experimentally reported values. Also the experimentally reported value of ANC for Fe${}_5$GeTe${}_2$ is close to our calculated value at room temperature, i.e., 0.10 A/Km.

9 pages, 7 figures