Colossal anomalous Nernst effect in a correlated noncentrosymmetric kagome ferromagnet

TL;DR

This paper reports a colossal anomalous Nernst effect in a correlated noncentrosymmetric kagome ferromagnet, UCo0.8Ru0.2Al, driven by strong electronic correlations and spin-orbit coupling, with implications for thermoelectric applications.

Contribution

It demonstrates a giant anomalous Nernst effect in a uranium-based ferromagnet, highlighting the role of electronic correlations and topological features like Weyl nodes.

Findings

Colossal ANE reaching 23 μV/K observed in UCo0.8Ru0.2Al.

Presence of at least 148 Weyl nodes near the Fermi level.

Strong correlation and spin-orbit coupling contribute to large thermoelectric response.

Abstract

Analogous to the Hall effect, the Nernst effect is the generation of a transverse voltage due to a temperature gradient in the presence of a perpendicular magnetic field. The Nernst effect has promise for thermoelectric applications and as a probe of electronic structure. In magnetic materials, a so-called anomalous Nernst effect (ANE) is possible in zero magnetic field. Here we report a colossal ANE reaching 23 $\mu$V/K in the ferromagnetic metal UCo$_{0.8}$Ru$_{0.2}$Al. Uranium's $5f$ electrons provide strong electronic correlations that lead to narrow bands, which are a known route to producing a large thermoelectric response. Additionally, the large nuclear charge of uranium generates strong spin-orbit coupling, which produces an intrinsic transverse response in this material due to the Berry curvature associated with the relativistic electronic structure. Theoretical calculations show that at least 148 Weyl nodes and two nodal lines exist within $\pm$ 60 meV of the Fermi level in UCo$_{0.8}$Ru$_{0.2}$Al. This work demonstrates that magnetic actinide materials can host strong Nernst and Hall responses due to their combined correlated and topological nature.