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Topological Lifshitz Transition-Induced Bipolarity of Anomalous Nernst Effect in Kagome Magnet YCo3
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DOI：10.1002/qute.202501010.png)
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Abstract
En 中文
The kagome lattice, renowned for hosting topological band structures and rich magnetic behaviors, offers an exceptional setting to investigate unconventional transport in magnetic topological systems. Controlling the polarity of the anomalous Nernst effect (ANE) is crucial for designing flexible thermoelectric devices, such as thermopiles, where the ability to switch the thermoelectric voltage sign can dramatically enhance energy conversion efficiency and output. Here, we demonstrate such a bipolar ANE in the kagome magnet YCo 3 ${\rm YCo}_3$ , driven by a temperature-induced topological Lifshitz transition. With a Curie temperature T C ≈ 225 K $T_C \approx 225\ \mathrm{K}$ , sizable anomalous Hall (AHE) and Nernst effects emerge below T C $T_C$ . Supported by the first-principles calculations, the AHE and ANE are suggested to be dominated by the intrinsic mechanism. Furthermore, the intrinsic anomalous Hall conductivity exhibits a piecewise-linear dependence on magnetization, with an abrupt slope change near 100 K, consistent with the Karplus–Luttinger mechanism. Concurrently, the anomalous Nernst coefficient S y x A $S^A_{yx}$ reverses its sign around the same temperature, realizing the crucial bipolarity. These anomalies could be interpreted as a topological Lifshitz transition, enabled by the evolution of Co moments that could shift the Fermi level relative to Weyl nodes. Our work reveals YCo 3 ${\rm YCo}_3$ as a prototypical kagome magnet where temperature and magnetism directly govern both Weyl node topology and the bipolar ANE, opening a pathway to magnetically control thermoelectric output in topological quantum materials.
Keywords:
anomalous Nernst effect
Kagome lattice
Lifshitz transition
magnetic Weyl semimetal
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