Exploring self-consistency of the equations of axion electrodynamics in Weyl semimetals
Exploring self-consistency of the equations of axion electrodynamics in Weyl semimetals
复制标题
DOI：
10.1103/physrevb.104.075202
复制
发表时间：
2021-03
影响因子：
3.7
通讯作者：
Kuangyin Deng;J. V. Van Dyke;D. Minic;J. Heremans;Edwin Barnes
中科院分区：
文献类型：
--
作者：
Kuangyin Deng;J. V. Van Dyke;D. Minic;J. Heremans;Edwin Barnes
最近的工作提供的证据表明，轴向异常可以出现在外尔半金属。如果是这样的话，那么外尔半金属的电磁响应应该由轴子电动力学方程控制。这些方程在线性响应的极限下捕获了手征磁性和异常霍尔效应，而在更高阶时，它们的解可以提供异常的可检测的电磁特征。在这项工作中，我们考虑三个版本的轴子电动力学已提出的外尔半金属文献。这些版本的不同之处在于手征磁项的形式，以及轴子是否被视为动力场。在每种情况下，我们寻找这些方程的简单的样品几何形状的解决方案，施加外部领域。我们发现，在由非动力学轴子产生的线性手征磁项的情况下，一般可以得到自洽解。在这种情况下，外尔半金属内部的磁场可以被显著放大，为实验提供可测试的特征。自洽的解决方案也可以获得动力学轴子，但只有在手征磁项消失的情况下相同。最后，对于文献中经常考虑的手征磁项的非线性形式，我们发现除了少数特殊情况外，没有自洽解。
Recent works have provided evidence that an axial anomaly can arise in Weyl semimetals. If this is the case, then the electromagnetic response of Weyl semimetals should be governed by the equations of axion electrodynamics. These equations capture both the chiral magnetic and anomalous Hall effects in the limit of linear response, while at higher orders their solutions can provide detectable electromagnetic signatures of the anomaly. In this work, we consider three versions of axion electrodynamics that have been proposed in the Weyl semimetal literature. These versions differ in the form of the chiral magnetic term and in whether or not the axion is treated as a dynamical field. In each case, we look for solutions to these equations for simple sample geometries subject to applied external fields. We find that in the case of a linear chiral magnetic term generated by a non-dynamical axion, self-consistent solutions can generally be obtained. In this case, the magnetic field inside of the Weyl semimetal can be magnified significantly, providing a testable signature for experiments. Self-consistent solutions can also be obtained for dynamical axions, but only in cases where the chiral magnetic term vanishes identically. Finally, for a nonlinear form of the chiral magnetic term frequently considered in the literature, we find that there are no self-consistent solutions aside from a few special cases.