Feng Tao, Wang Panshuo, Han Zhijia, Zhou Liang, Zhang Wenqing, Liu Qihang, Liu Weishu
Department of Materials Science and Engineering, Southern University of Science and Technology, Shenzhen, 518055, China.
Department of Physics and Shenzhen Institute for Quantum Science & Engineering, Southern University of Science and Technology, Shenzhen, 518055, China.
Adv Mater. 2022 May;34(19):e2200931. doi: 10.1002/adma.202200931. Epub 2022 Apr 4.
Topological semimetals provide new opportunities for exploring novel thermoelectric phenomena, owing to their exotic and nontrivial electronic structure topology around the Fermi surface. Herein, the discovery of large transverse and longitudinal magneto-thermoelectric (MTE) effects in Mg Bi is reported and predicted to be a type-II nodal-line semimetal in the absence of spin-orbit coupling (SOC). The maximum transverse power factor is 2182 μW m K at 13.5 K and 6 Tesla. The longitudinal power factor reaches up to 3043 μW m K , which is 20 times higher than that in a zero-strength magnetic field and is also comparable to state-of-the-art MTE materials. By compensating the Mg loss in Mg-rich conditions for tuning the carrier concentration close to intrinsic state, the sample fabricated in this study exhibits a large linear non-saturating magnetoresistance of 940% under a field of 14 Tesla. Using density functional calculations, the authors attribute the underlying mechanism to the parent linear-dispersed nodal-line electronic structure without SOC and the anisotropic Fermi surface shape with SOC, highlighting the essential role of high carrier mobility and open electron orbits in the moment space. This work offers a new avenue toward highly efficient MTE materials through defect engineering in polycrystalline topological semimetals.
拓扑半金属因其费米面周围奇异且非平凡的电子结构拓扑，为探索新型热电现象提供了新机遇。在此，报道了在MgBi中发现的大横向和纵向磁热电（MTE）效应，并预测其在无自旋轨道耦合（SOC）时为II型节线半金属。在13.5K和6特斯拉时，最大横向功率因子为2182μW m K。纵向功率因子高达3043μW m K，比零磁场强度时高20倍，且与最先进的MTE材料相当。通过在富镁条件下补偿镁损失以将载流子浓度调节至接近本征态，本研究制备的样品在14特斯拉磁场下表现出940%的大线性非饱和磁电阻。通过密度泛函计算，作者将其潜在机制归因于无SOC时的母体线性色散节线电子结构以及有SOC时的各向异性费米面形状，突出了高载流子迁移率和动量空间中开放电子轨道的重要作用。这项工作通过多晶拓扑半金属中的缺陷工程为高效MTE材料开辟了一条新途径。
