Large power factor, anomalous Nernst effect, and temperature-dependent thermoelectric quantum oscillations in the magnetic Weyl semimetal NdAlSi
Qingxin Dong, Jinfeng Wang, Libo Zhang, Jianli Bai, Qiao-Yu Liu, Jingwen Cheng, Pin-Yu Liu, Cundong Li, Junsen Xiang, Zhi-An Ren, Peijie Sun, Genfu Chen
Abstract
Magnetic topological materials have attracted much attention due to the interplay between magnetism and topological electronic band structure, which may not only generate new exotic quantum states but also bring great potential applications. Here, we present Seebeck and Nernst effects in the magnetic Weyl semimetal NdAlSi as a function of temperature and magnetic field. We find that the power factor reaches $15\phantom{\rule{0.28em}{0ex}}\textmu{}\mathrm{W}\phantom{\rule{0.28em}{0ex}}\mathrm{c}{\mathrm{m}}^{\ensuremath{-}1}\phantom{\rule{0.28em}{0ex}}{\mathrm{K}}^{\ensuremath{-}2}$ at 300 K and zero field, which compare favorably with those of traditional heavily doped semiconductors. We also find that the anomalous Nernst signals dominate the magneto-thermoelectric properties. In particular, we find that both Seebeck and Nernst effects oscillate clearly as a function of temperature in a constant magnetic field, in addition to the ordinary quantum oscillations with periodicity in inverse magnetic field at a constant temperature. Such new type of temperature-induced oscillations only appears at the narrow field-induced crossover region from a paramagnetic to a polarized paramagnetic phase and arise from the band exchange splitting due to the strong exchange interaction between conductive electrons and $4f$ electrons in NdAlSi. Our findings not only demonstrate the potential application of NdAlSi, but also greatly enrich the available quantum phenomena in thermoelectric response.