Exploring the apparent violation of the Mott relation in a noncentrosymmetric kagome ferromagnet

TL;DR

This study investigates doping-dependent transport in a topological metal, revealing that the Mott relation, often expected to hold, can appear violated but is actually satisfied when considering the evolving electronic structure.

Contribution

The paper introduces a model explaining how doping influences topological Weyl points and magnetism, clarifying the apparent violation of the Mott relation in a correlated topological metal.

Findings

Weyl points are pinned to the Fermi energy by a correlated flat band.

The model explains doping-dependent anomalous Hall and Nernst conductivities.

The Mott relation is satisfied at each doping level when considering the electronic structure.

Abstract

In magnetic topological materials, time-reversal symmetry breaking gives rise to topological point and line nodes with distinctive signatures in the anomalous Hall and anomalous Nernst conductivity that satisfy the well-known Mott relation. However, this relationship can fail for doping-dependent transport measurements of materials with complex magnetism, topology, and electronic correlations. In this work, we present transport measurements of the correlated topological metal UCoAl doped with Ru, which appear to violate the Mott relation. We develop a model that captures the evolution of Stoner magnetism and topological Weyl points as a function of doping. Using this model, we show how the correlated flat band in this material pins the Weyl points to the Fermi energy, and demonstrate how this explains the unusual doping-dependent behavior of the anomalous Hall and anomalous Nernst conductivities in this material, while the Mott relation is in fact satisfied at each doping level.