Topological properties and anomalous transport in van der Waals ferromagnets Fe n GeTe2: a comparative study

Abstract

Recently synthesized topological van der Waals (vdW) Fe n GeTe2 (n=3,4, and 5) series of compounds have drawn a lot of research interest due to their interesting magnetic properties and anomalous transport behavior. However, understanding the topological aspect of these materials’ electronic band structure is either scant or absent in the literature. In this work, we perform a comparative study of the electronic structure of all three materials to understand their topological properties and their effect on transport properties using the first-principles calculations and to derive the effective tight-binding model for these systems. All three systems exhibit ferromagnetic behavior, and the contribution of various Fe d-orbitals are also studied. Spin-orbit coupling (SOC) causes the degeneracy to be lifted and results in a finite Berry curvature (BC). Finite BC contributes to the intrinsic anomalous Hall conductivity (AHC) and Nernst conductivity (ANC) of these systems. We show that Fe3GeTe2 and Fe5GeTe2 have similar nodal line formations, while Fe4GeTe2 exhibits nodal points close to Fermi energy E F . We calculate AHC (σ xy ) at zero temperature and ANC (α xy ) at room temperature for n = 3, 4 and 5 and find that our values are consistent with transport and magnetic measurement.