Abstract
An axion is a hypothetical elementary particle which was initially postulated to solve the charge conjugation-parity problem in particle physics. Interestingly, the axion state has emerged in the effective theory of topological insulators and has attracted extensive attention in condensed matter physics. Time-reversal or inversion symmetry constrains the axion field to be quantized. When both the time-reversal and inversion symmetries are broken by, say, an antiferromagnetic order, the axion field could become unquantized and dynamical along with magnetic fluctuations, which is termed the dynamical axion field. Here, we reveal that a wide class of topological-insulator-based dynamical axion states could be distinguished from the normal-insulator-based ones by a hidden quantity derived from the pseudospin Chern number. Motivated by recent research on the family of materials, we further show that such topological-insulator-based dynamical axion states can be hopefully achieved in -based heterostructures, which should greatly facilitate the study of axion electrodynamics in condensed matter physics.
- Received 9 November 2019
- Accepted 4 February 2020
DOI:https://doi.org/10.1103/PhysRevB.101.081109
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