PbTe中态密度的急剧增加接近能带结构中的鞍点
A sharp increase in the density of states in PbTe approaching a saddle point in the band structure
摘要：
PbTe是具有$zT$的领先的中范围热电材料，该材料已经通过能带工程等方法得到增强。在这里，我们提出了一个实验研究的霍尔效应，量子振荡，比热，和电子探针分析，探讨了PbTe重掺杂的电子结构的演变与“理想”的受体Na的溶解度极限。我们确定了两个现象学的变化，发病的电子结构偏离凯恩型分散在180毫电子伏左右，一个质变的霍尔效应的场依赖性的高场极限的增加和费米学的变化，以及作为能量的函数的态密度急剧增加。在考虑了所观察到的现象学的三个可能的起源之后，我们得出结论，最可能的来源是在接近能带结构中的鞍点时$L$口袋的非椭球性，这直接由我们的量子振荡测量证明。比较密度泛函理论的计算意味着，这种演变的电子结构可能是一个关键的贡献者在PbTe的大的热电势。
英文摘要：
PbTe is a leading mid-range thermoelectric material with a $zT$ that has been enhanced by, amongst other methods, band engineering. Here we present an experimental study of the Hall effect, quantum oscillations, specific heat, and electron microprobe analysis that explores the evolution of the electronic structure of PbTe heavily doped with the `ideal' acceptor Na up to the solubility limit. We identify two phenomenological changes that onset as the electronic structure deviates from a Kane-type dispersion at around 180meV; a qualitative change in the field dependence of the Hall effect indicative of an increase in the high-field limit and a change in the Fermiology, and a sharp increase in the density of states as a function of energy. Following consideration of three possible origins for the observed phenomenology we conclude that the most likely source is non-ellipsoidicity of the $L$-pocket upon approach to a saddle point in the band structure, which is evidenced directly by our quantum oscillation measurements. Comparison to density functional theory calculations imply that this evolution of the electronic structure may be a key contributor to the large thermopower in PbTe.
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