Giant anomalous Nernst signal in the antiferromagnet YbMnBi2

Yu Pan,Johannes Gooth,Joseph P Heremans,Mengyu Yao,Congcong Le,Sarah J Watzman,Bin He,Claudia Felser,Yan Sun

doi:10.1038/s41563-021-01149-2

Abstract

A large anomalous Nernst effect (ANE) is crucial for thermoelectric energy conversion applications because the associated unique transverse geometry facilitates module fabrication. Topological ferromagnets with large Berry curvatures show large ANEs; however, they face drawbacks such as strong magnetic disturbances and low mobility due to high magnetization. Herein, we demonstrate that YbMnBi2, a canted antiferromagnet, has a large ANE conductivity of ~10 A m−1 K−1 that surpasses large values observed in other ferromagnets (3–5 A m−1 K−1). The canted spin structure of Mn guarantees a non-zero Berry curvature, but generates only a weak magnetization three orders of magnitude lower than that of general ferromagnets. The heavy Bi with a large spin–orbit coupling enables a large ANE and low thermal conductivity, whereas its highly dispersive px/y orbitals ensure low resistivity. The high anomalous transverse thermoelectric performance and extremely small magnetization make YbMnBi2 an excellent candidate for transverse thermoelectrics.

Highlights

Topological electronic structures lay the foundation for new functionalities and are crucial for various applications, including thermoelectric energy conversion[1,2,3]
The large spin–orbit coupling (SOC) from Bi is critical for band topology, transverse transport response and low thermal conductivity
The YbMnBi2 canted antiferromagnet has much smaller magnetization and inherent stray fields than other ferromagnets. All of these features demonstrate that YbMnBi2 could provide a new material platform beyond ferromagnets for transverse thermoelectric applications

Summary

Introduction

Topological electronic structures lay the foundation for new functionalities and are crucial for various applications, including thermoelectric energy conversion[1,2,3]. With the emergence of topological semimetals, the anomalous Nernst effect (ANE) has attracted increasing attention for transverse thermoelectric applications[2,3,6,7,8,9,10]. YbMnBi2, as a canted antiferromagnet, can simultaneously realize broken time-reversal symmetry and relatively low resistivity with light band conduction.

Results

Conclusion