Giant anomalous Nernst effect and quantum-critical scaling in a ferromagnetic semimetal
Giant anomalous Nernst effect and quantum-critical scaling in a ferromagnetic semimetal
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DOI：
10.1038/s41567-018-0225-6
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发表时间：
2018-11-01
期刊：
影响因子：
19.6
通讯作者：
Nakatsuji, Satoru
中科院分区：
文献类型：
--
作者：
Sakai, Akito;Mizuta, Yo Pierre;Nakatsuji, Satoru
在导电铁磁体中，电子波函数的非平凡几何结构或贝里曲率可以驱动反常能斯特效应（反常能斯特效应是指垂直于磁化强度和外加温度梯度的电压的产生）（1,2）。在这里，我们报告了在室温下在全heusler铁磁体Co2MnGa中观察到的巨大异常能司特效应，比之前报道的磁性导体的最大值大一个数量级（3,4）。我们的数值和分析计算表明，在i型和ii型磁性Weyl费米子（5-7）之间接近量子Lifshitz跃迁是观察到的- Tlog(T)行为的原因，T表示温度，以及横向热电导电性的增强值。实验和数值计算中热电响应的温度依赖性可以用低能有效理论在十多年温度下预测的量子临界尺度函数来理解。此外，观察到的不饱和正纵向磁导或手性异常（8-10）也为Co2MnGa中存在Weyl费米子（11,12）提供了证据。
In conducting ferromagnets, an anomalous Nernst effect-the generation of an electric voltage perpendicular to both the magnetization and an applied temperature gradient-can be driven by the nontrivial geometric structure, or Berry curvature, of the wavefunction of the electrons(1,2). Here, we report the observation of a giant anomalous Nernst effect at room temperature in the full-Heusler ferromagnet Co2MnGa, an order of magnitude larger than the previous maximum value reported for a magnetic conductor(3,4). Our numerical and analytical calculations indicate that the proximity to a quantum Lifshitz transition between type-I and type-II magnetic Weyl fermions(5-7) is responsible for the observed - Tlog(T) behaviour, with T denoting the temperature, and the enhanced value of the transverse thermoelectric conductivity. The temperature dependence of the thermoelectric response in experiments and numerical calculations can be understood in terms of a quantum critical-scaling function predicted by the low-energy effective theory over more than a decade of temperatures. Moreover, the observation of an unsaturated positive longitudinal magnetoconductance, or chiral anomaly(8-10), also provides evidence for the existence of Weyl fermions(11,12) in Co2MnGa.