TY - JOUR

T1 - Axion electrodynamics in topological materials

AU - Sekine, Akihiko

AU - Nomura, Kentaro

N1 - Funding Information:
A.S. acknowledges valuable discussions with Koji Ishiwata and Makoto Naka. A.S. is supported by the Special Postdoctoral Researcher Program of RIKEN. K.N. is supported by JST CREST Grant No. JP-MJCR18T2 and JSPS KAKENHI Grant No. JP20H01830.
Publisher Copyright:
© 2021 Author(s).

PY - 2021/4/14

Y1 - 2021/4/14

N2 - One of the intriguing properties characteristic to three-dimensional topological materials is the topological magnetoelectric phenomena arising from a topological term called the θ term. Such magnetoelectric phenomena are often termed the axion electrodynamics since the θ 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 the θ term.

AB - One of the intriguing properties characteristic to three-dimensional topological materials is the topological magnetoelectric phenomena arising from a topological term called the θ term. Such magnetoelectric phenomena are often termed the axion electrodynamics since the θ 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 the θ term.

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U2 - 10.1063/5.0038804

DO - 10.1063/5.0038804

M3 - Article

AN - SCOPUS:85103892881

VL - 129

JO - Journal of Applied Physics

JF - Journal of Applied Physics

SN - 0021-8979

IS - 14

M1 - 141101

ER -