Enhancement of the transverse thermoelectric conductivity originating from stationary points in nodal lines
Enhancement of the transverse thermoelectric conductivity originating from stationary points in nodal lines
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DOI：
10.1103/physrevb.102.205128
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发表时间：
2020-11-23
影响因子：
3.7
通讯作者：
Arita, Ryotaro
中科院分区：
文献类型：
--
作者：
Minami, Susumu;Ishii, Fumiyuki;Arita, Ryotaro
受最近在 Co2MnGa、Fe3X (X=A1, Ga) 和 Co3Sn2S2 中发现的巨大反常能斯特效应的启发，我们进行了第一性原理研究，以阐明这些铁磁体中横向热电导率 a ii 增强的根源。对 alpha(ij) 的内在贡献可以用费米能级周围的贝里曲率 Omega 来理解，并且 Omega 沿着布里渊区的节点线（在没有自旋轨道耦合的情况下是无间隙的）非常大。我们发现，不仅韦尔点，而且驻点在节点线的能量色散中都起着至关重要的作用。驻点在投影到节点线上的态密度中形成尖锐的峰值，清楚地识别了 alpha(ij) 最显着增强的特征费米能量。我们还发现 alpha(ij)/T 打破了莫特关系，并在这些能量下表现出特殊的温度依赖性。目前的结果表明，驻点将为我们提供有用的指导原则来设计具有大反常能斯特效应的磁体。
Motivated by the recent discovery of a large anomalous Nernst effect in Co2MnGa, Fe3X (X=A1, Ga) and Co3Sn2S2, we performed a first-principles study to clarify the origin of the enhancement of the transverse thermoelectric conductivity a ii in these ferromagnets. The intrinsic contribution to alpha(ij) can be understood in terms of the Berry curvature Omega around the Fermi level, and Omega is singularly large along nodal lines (which are gapless in the absence of the spin-orbit coupling) in the Brillouin zone. We find that not only the Weyl points but also stationary points in the energy dispersion of the nodal lines play a crucial role. The stationary points make sharp peaks in the density of states projected onto the nodal line, clearly identifying the characteristic Fermi energies at which alpha(ij) is most dramatically enhanced. We also find that alpha(ij)/T breaks the Mott relation and show a peculiar temperature dependence at these energies. The present results suggest that the stationary points will give us a useful guiding principle to design magnets showing a large anomalous Nernst effect.