Ultrahigh Anomalous Nernst Thermopower and Thermal Hall Angle in YbMnBi2

TL;DR

This study reports that YbMnBi2 exhibits the highest anomalous Nernst thermopower among magnetic materials, driven by topological band effects, with significant thermal Hall angles across a broad temperature range.

Contribution

It demonstrates that YbMnBi2's large anomalous Nernst effect is due to topological band structure and magnetic order, surpassing previous materials in thermoelectric performance.

Findings

YbMnBi2 shows a Nernst thermopower of around 110 μV/K at 254 K.

An observable thermal Hall angle of 0.02 to 0.06 across 40 K to 310 K.

Large anomalous Nernst effect driven by topological band contributions.

Abstract

Thermoelectrics (TEs) are solid-state devices that can realize heat-electricity conversion. Transverse TEs require materials with a large Nernst effect, which typically requires a strong applied magnetic field. However, topological materials with magnetic order offer an alternative pathway for achieving large Nernst via the anomalous Hall effect and the accompanying anomalous Nernst effect (ANE) that arise from band topology. Here, we show that YbMnBi2 with a low Hall density and a chemical potential near the Weyl points has, to the best of our knowledge, the highest ANE-dominated Nernst thermopower of any magnetic material, with $S_{yx}$ around 110 $\mu$V/K ($T$ = 254 K, 5 T < $|\mu_0 H|$ < 9 T applied along the spin canting direction), due to the synergism between classical contributions from filled electron bands, large Hall conductivity of topological origin, and large resistivity anisotropy. An appreciable thermal Hall angle of $0.02 < (\nabla_y T)/(\nabla_x T) < 0.06$ was observed (40 K < $T$ < 310 K, $\mu_0 H$ = 9 T).