Axion electrodynamics in topological materials
Axion electrodynamics in topological materials
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DOI：
10.1063/5.0038804
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发表时间：
2021-04-14
影响因子：
3.2
通讯作者：
Nomura, Kentaro
中科院分区：
文献类型：
--
作者：
Sekine, Akihiko;Nomura, Kentaro
三维拓扑材料的一个有趣的特性是由一种称为theta项的拓扑项产生的拓扑磁电现象。这种磁电现象通常被称为轴子电动力学，因为theta项具有与描述假设的基本粒子、轴子和光子之间的耦合的作用完全相同的形式。轴子是大约40年前提出的，用来解决量子色动力学中所谓的强CP问题，现在被认为是暗物质的候选者。在本教程中，我们概述了三维拓扑材料中轴子电动力学的理论和实验研究。从三维时反不变拓扑绝缘子中的拓扑磁电效应出发，描述了实现需要磁有序的静态和动态轴子绝缘子的基本性质。我们还讨论了Weyl半金属的电磁响应，重点讨论了手征反常。我们将凝聚态中的轴子电动力学的概念推广到拓扑超导体，它对外场的响应可以用一个类似于theta项的引力拓扑项来描述。
One of the intriguing properties characteristic to three-dimensional topological materials is the topological magnetoelectric phenomena arising from a topological term called thetheta term. Such magnetoelectric phenomena are often termed the axion electrodynamics since thetheta term has exactly the same form as the action describing the coupling between a hypothetical elementary particle, axion, and a photon. The axion was proposed about 40 years ago to solve the so-called strong CP problem in quantum chromodynamics and is now considered a candidate for dark matter. In this Tutorial, we overview theoretical and experimental studies on the axion electrodynamics in three-dimensional topological materials. Starting from the topological magnetoelectric effect in three-dimensional time-reversal invariant topological insulators, we describe the basic properties of static and dynamical axion insulators whose realizations require magnetic orderings. We also discuss the electromagnetic responses of Weyl semimetals with a focus on the chiral anomaly. We extend the concept of the axion electrodynamics in condensed matter to topological superconductors, whose responses to external fields can be described by a gravitational topological term analogous to thetheta term.