Cheng Bing, Schumann Timo, Stemmer Susanne, Armitage N P
Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218, USA.
Materials Department, University of California, Santa Barbara, Santa Barbara, CA 93106, USA.
Sci Adv. 2021 Apr 16;7(16). doi: 10.1126/sciadv.abg0914. Print 2021 Apr.
The linear band crossings of 3D Dirac and Weyl semimetals are characterized by a charge chirality, the parallel or antiparallel locking of electron spin to its momentum. These materials are believed to exhibit an E · B chiral magnetic effect that is associated with the near conservation of chiral charge. Here, we use magneto-terahertz spectroscopy to study epitaxial CdAs films and extract their conductivities σ(ω) as a function of E · B. As field is applied, we observe a markedly sharp Drude response that rises out of the broader background. Its appearance is a definitive signature of a new transport channel and consistent with the chiral response, with its spectral weight a measure of the net chiral charge and width a measure of the scattering rate between chiral species. The field independence of the chiral relaxation establishes that it is set by the approximate conservation of the isospin that labels the crystalline point-group representations.
三维狄拉克和外尔半金属的线性能带交叉由电荷手性来表征，即电子自旋与其动量的平行或反平行锁定。这些材料被认为会表现出一种与手性电荷近乎守恒相关的E·B手性磁效应。在此，我们使用磁太赫兹光谱来研究外延CdAs薄膜，并提取其作为E·B函数的电导率σ(ω)。施加磁场时，我们观察到一个明显尖锐的德鲁德响应，它从更宽的背景中显现出来。其出现是一个新传输通道的确切标志，并且与手性响应一致，其光谱权重是净手性电荷的量度，宽度是手性物种之间散射率的量度。手性弛豫的场独立性表明，它是由标记晶体点群表示的同位旋近似守恒所设定的。
