Npj Comput. Mater.: 转热为电的材料—可从电子结构逆向设计？

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然而其热电转换效率却是制约其实际应用的瓶颈因素。传统的反常能斯特效应材料的发现要么集中在特定材料体系比如哈斯勒金属，要么是偶然发现。如果从电子结构逆向设计的角度来寻找大的反常能斯特效应材料，可大大提高新候选体系的发现速度。

Fig. 2 Modulation of ANC for the four-band Dirac model with Zeeman term.

来自南方科技大学的刘奇航教授团队，从理论上证明了在塞曼场下，一对狄拉克节点会呈现出随化学势变化奇函数分布、具有双峰特征的反常霍尔电导率曲线，以及补偿的载流子特性，从而获得比传统的，仅有一对外尔点的两带外尔半金属模型有300%增强的反常能斯特热电导率。结合上述能带模型及第一性原理计算，该研究提供了两个实际的候选材料：狄拉克半金属Na3Bi和NaTeAu。在塞曼场下，它们在费米能级附近的反常能斯特热电导率分别可达到0.4 Am^(-1) K^(-1) 和 1.3 Am^(-1) K^(-1)。其中NaTeAu的反常霍尔电导率曲线随化学势变化呈双峰特征，从而在费米能级附近有一个反常能斯特热电导率的极大值，与塞曼场下的狄拉克能带模型相符。

Fig. 3 Electronic structures and transport properties of Na3Bi under Zeeman field.

进一步地，该团队通过把NaTeAu中50%的Na替换为Fe，获得了具有塞曼劈裂的本征铁磁拓扑材料NaFeTe2Au2，它在费米能级附近展现出高达3.7 Am^(-1) K^(-1)的反常能斯特热电导率。该研究还设计了一种全哈斯勒铁磁材料Co2PdGe，同样在费米能级附近有高达6.2 Am^(-1) K^(-1)的反常能斯特热电导率。

总之，该研究提供了一种功能材料设计思路，首先设计特定的能带结构然后筛选出符合这种电子结构的材料，这将提升新候选材料的发现速度。该文近期发表于npj Computational Materials 9: 203 (2023)，英文标题与摘要如下，点击左下角“阅读原文”可以自由获取论文PDF。

Rational design of large anomalous Nernst effect in Dirac semimetals 

Panshuo Wang, Zongxiang Hu, Xiaosong Wu & Qihang Liu 

Anomalous Nernst effect generates a transverse voltage perpendicular to the temperature gradient. It has several advantages compared with the longitudinal thermoelectricity for energy conversion, such as decoupling of electronic and thermal transports, higher flexibility, and simpler lateral structure. However, a design principle beyond specific materials systems for obtaining a large anomalous Nernst conductivity (ANC) is still absent. In this work, we theoretically demonstrate that a pair of Dirac nodes under a Zeeman field manifests an odd-distributed, double-peak anomalous Hall conductivity curve with respect to the chemical potential and a compensated carrier feature, leading to an enhanced ANC compared with that of a simple Weyl semimetal with two Weyl nodes. Based on first-principles calculations, we then provide two Dirac semimetal candidates, i.e., Na3Bi and NaTeAu, and show that under a Zeeman field they exhibit a sizable ANC value of 0.4 Am^(-1) K^(-1) and 1.3 Am^(-1) K^(-1), respectively, near the Fermi level. Such approach is also applicable to ferromagnetic materials with intrinsic Zeeman splitting, as exemplified by a hypothetical alloy NaFeTe2Au2, exhibiting an ANC as high as 3.7 Am^(-1) K^(-1) at the Fermi level. Our work provides a design principle with a prototype band structure for enhanced ANC pinning at Fermi level, shedding light on the inverse design of other specific functional materials based on electronic structure.