A First Principle Study on Anomalous Hall and Nernst Effects in Ideal Weyl Semimetal EuCd₂As₂

Wei-Kuo Li^1*, Guang-Yu Guo^1,2

¹Department of Physics, National Taiwan University, Taipei 10617, Taiwan
²Physics Division, National Center for Theoretical Sciences, Taipei 10617, Taiwan

* Presenter:Wei-Kuo Li, email:weikuo38@gmail.com

The anomalous Nernst effect probes the transverse current driven by thermal gradient in a magnetic metal. It is closely related to the Berry curvature of the states near the Fermi energy (EF). Ferromagnetic EuCd₂As₂ (ECA) is a semimetal featuring Weyl-fermion dispersions near Ewp = 25 meV above EF. It would be interesting to study anomalous Nernst effect since it probes of Berry curvature induced by Weyl fermion states near the Fermi energy. In this work, we present a theoretical investigation on magnetism, electronic, anomalous Hall and Nernst effects of ECA, based on the density functional theory with the generalized gradient approximation plus onsite Coulomb repulsion scheme. The calculated anomalous Hall conductivity at Ewp is 27 S/cm. It can be further increased to 64 S/cm by lowering to EF - 70 meV. Such large change of anomalous Hall conductivity in such small energy window hints for large anomalous Nernst effect. Indeed, the calculated anomalous Nernst conductivity α/T ≈ 1.5 mA/m-K², which is large compared to that of ferromagnetic iron α/T ≈ 1.6 mA/m-K². The large anomalous Nernst effect manifests the importance of the band topology of Weyl states near the Fermi energy.

Keywords: Weyl semimetal, anomalous Hall effect, anomalous Nernst effect, Berry curvature