Giant Anomalous Nernst Effect Coefficient and Thermal Hall Angle in the Direction of Spin Canting in Antiferromagnet YbMnBi₂

A large anomalous Nernst effect (ANE) has been sought after for thermoelectric applications in transverse geometry, as it contributes to greatly simplified thermoelectric device fabrication. YbMnBi₂, a topological antiferromagnet (AFM), was demonstrated to have a large ANE thermopower of ~ 6 µV K^-1,with a magnetic field B applied along [100], temperature gradient∇T applied along [010] and Nernst voltage V_N measured along [001], which was claimed to outshine all the other ANE thermopowers that had ever been reported in antiferromagnets¹. In this study, we present that in a different configuration in which B is applied along canted antiferromagnetic moment direction [110],∇T along [1-10] and V_N along [001], a remarkably large ANE coefficient of at least 30 µV K^-1 was observed and reproduced in different samples, which is probably ranked as the largest ANE thermopower reported in AFMs so far. The thermal Hall angle is also anomalously large (∇_yT/∇_xT > 0.05) across the experiment range of 40 K ~ 300 K and shows a step in field at certain temperatures, suggesting the existence of an Anomalous Thermal Hall Effect (ATHE). The relatively low carrier density, which puts the chemical potential near the Weyl points, and high carrier mobility of these samples are key to these observations. The carrier polarity flip at high fields points at the topological origin of these anomalous transport phenomena.

1. Pan, Y., Le, C., He, B. et al. Giant anomalous Nernst signal in the antiferromagnet YbMnBi₂. Nat. Mater. 21, 203–209 (2022).