Flavors of magnetic noise in quantum materials
Flavors of magnetic noise in quantum materials
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DOI：
10.1103/physrevb.106.l081122
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发表时间：
2021-08
影响因子：
3.7
通讯作者：
Shu Zhang;Y. Tserkovnyak
中科院分区：
文献类型：
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作者：
Shu Zhang;Y. Tserkovnyak
量子材料中电子带结构的复杂性为输运提供了新的电荷中性自由度，Weyl半金属（WSMs）中的谷（轴）自由度就是一个很有前途的例子。通过利用材料附近产生的磁噪声的频率依赖性，可以对其输运特性进行无创探测。在这项工作中，我们使用系统的朗格万方法研究了与扩散输运一般相关的磁噪声。以磁性wsm的最小模型为例，我们证明了电荷电流、谷电流和磁阶的热波动会产生具有明显不同光谱特征的磁噪声，这为分离它们的贡献提供了理论指导。我们的方法可以扩展到量子材料中其他输运自由度产生的磁噪声及其光谱特征的研究。本文介绍了磁性Weyl半金属中电荷、谷和自旋自由度的波动通过不同的产生核产生磁噪声的细节。具体来说，假设材料尺寸远大于d，我们研究在NV中心位置r NV = (0,0,d)处的磁场B （r NV, t）是由占据z≤0的半空间Ω的材料产生的
The complexity of electronic band structures in quantum materials offers new charge-neutral degrees of freedom stable for transport, a promising example being the valley (axial) degree of freedom in Weyl semimetals (WSMs). A noninvasive probe of their transport properties is possible by exploiting the frequency dependence of the magnetic noise generated in the vicinity of the material. In this work, we investigate the magnetic noise generically associated with diffusive transport using a systematic Langevin approach. Taking a minimal model of magnetic WSMs for demonstration, we show that thermal fluctuations of the charge current, the valley current, and the magnetic order can give rise to magnetic noise with distinctively different spectral characters, which provide a theoretical guidance to separate their contributions. Our approach is extendable to the study of magnetic noise and its spectral features arising from other transport degrees of freedom in quantum materials. In this we present the details on the generation of the magnetic noise by the fluctuations of the charge, valley, and spin degrees of freedom in a magnetic Weyl semimetal, via different generating kernels. Specifically, we look into the magnetic field B ( r NV , t ) at the position of the NV center r NV = (0 , 0 , d ) generated by the material occupying the half space Ω with z ≤ 0, assuming the material dimensions are much larger than d