WTe₂ is one of a series of recently discovered high mobility semimetals, some of whose properties are characteristic of topological Dirac or Weyl metals. One of its most interesting properties is the unsaturated giant magnetoresistance that it exhibits at low temperatures. An important question is the degree to which this property can be ascribed to a conventional semimetallic model in which a highly compensated, high mobility metal exhibits large magnetoresistance. Here, we show that the longitudinal thermopower (Seebeck effect) of semimetallic WTe₂ exfoliated flakes exhibits periodic sign changes about zero with increasing magnetic field that indicates distinct electron and hole Landau levels and nearly fully compensated electron and hole carrier densities. However, inconsistent with a conventional semimetallic picture, we find a rapid enhancement of the Nernst effect at low temperatures that is nonlinear in magnetic field, which is consistent with Weyl points in proximity to the Fermi energy. Hence, we demonstrate the role played by the Weyl character of WTe₂ in its transport properties.

中文翻译：

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II型Weyl半金属WTe _2的热能和非常规能斯特效应

WTe ₂是最近发现的一系列高迁移率半金属之一，其某些特性是拓扑狄拉克或Weyl金属的特征。它最有趣的特性之一是它在低温下表现出的不饱和巨磁电阻。一个重要的问题是该特性可归因于常规半金属模型的程度，在常规半金属模型中，高度补偿的高迁移率金属表现出较大的磁阻。在这里，我们显示了半金属WTe ₂的纵向热功率（塞贝克效应）剥落的薄片随着磁场的增加而表现出大约为零的周期性符号变化，这表明电子和空穴的朗道能级不同，并且电子和空穴的载流子密度几乎得到了补偿。但是，与常规的半金属图片不一致，我们发现在低温下能斯特效应迅速增强，这在磁场中是非线性的，这与接近费米能量的Weyl点是一致的。因此，我们证明了WTe ₂的Weyl特性在其运输特性中所起的作用。