Axion Instability and Nonlinear Electromagnetic Effect

Imaeda, Tatsushi; Kawaguchi, Yuki; Tanaka, Yukio; Sato, Masatoshi

doi:10.7566/jpsj.88.024402

Cited by 15 publications

(20 citation statements)

References 39 publications

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“…In the present basis, the time-reversal operator and spatial inversion (parity) operator are given by T = 1 ⊗ (−iσ 2 )K (K is the complex conjugation operator) and P = τ 1 ⊗ 1, respectively. We have introduced the hopping strength anisotropy δt 1 due to the lattice distortion along the [111] direction. Namely, we have set such that t i j = t + δt 1 for the [111] direction, and t i j = t for the other three directions.…”

Section: Fu-kane-mele-hubbard Model On a Diamond Latticementioning

confidence: 99%

“…We have introduced the hopping strength anisotropy δt 1 due to the lattice distortion along the [111] direction. Namely, we have set such that t i j = t + δt 1 for the [111] direction, and t i j = t for the other three directions. When δt 1 = 0, the system is a semimetal, i.e., the energy bands touch at the three points X r = 2π(δ rx , δ ry , δ rz ) (r = x, y, z).…”

Section: Fu-kane-mele-hubbard Model On a Diamond Latticementioning

confidence: 99%

“…In the numerical result (Fig. 18), in which the Néel vector is set to be in the [111] direction as n x = n y = n z ≡ h/U, the value of θ has a linear dependence on β ∝ h/δt 1 when Un f /δt 1 1 (i.e., around β = 0 or β = π). Thus, the analytical result [Eq.…”

Section: Fu-kane-mele-hubbard Model On a Diamond Latticementioning

confidence: 99%

“…In the following, we consider the consequences of the realization of a dynamical axion field in condensed matter. Among several theoretical studies on the emergent phenomena from a dynamical axion field 17,104,[108][109][110][111] , we particularly focus on three studies on the responses of topological antiferromagnetic insulators with a dynamical axion field δ θ (r,t) to external electric and magnetic fields.…”

Section: B Emergent Phenomena From Axion Electrodynamicsmentioning

confidence: 99%

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Axion electrodynamics in topological materials

Sekine

Nomura

2021

Journal of Applied Physics

176

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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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Section: Fu-kane-mele-hubbard Model On a Diamond Latticementioning

confidence: 99%

Section: Fu-kane-mele-hubbard Model On a Diamond Latticementioning

confidence: 99%

Section: Fu-kane-mele-hubbard Model On a Diamond Latticementioning

confidence: 99%

Section: B Emergent Phenomena From Axion Electrodynamicsmentioning

confidence: 99%

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Axion electrodynamics in topological materials

Sekine

Nomura

2021

Journal of Applied Physics

176

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“…to obtain a set of modified Maxwell's equations [8], which indicates DAF naturally couples with the light. Many exotic electromagnetic phenomena were predicted for DAF systems, such as, axion polariton [5], the chiral magnetic effect [9][10][11], and so on [12][13][14][15]. Interestingly, it was also proposed to detect axion dark matter in the universe [16].…”

mentioning

confidence: 99%

Unconventional level attraction in cavity axion polariton of antiferromagnetic topological insulator

Xiao¹,

Wang²,

Wang³

et al. 2020

Preprint

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Strong coupling between cavity photons and various excitations in condensed matters boosts the field of light-matter interaction and generates several exciting sub-fields, such as cavity optomechanics and cavity magnon polariton. Axion quasiparticles, emerging in topological insulators, were predicted to strongly couple with the light and generate the so-called axion polariton. Here, we demonstrate that there arises a gapless level attraction in cavity axion polariton of antiferromagnetic topological insulators, which originates from a nonlinear interaction between axion and the odd-order resonance of cavity. Such a novel level attraction is essentially different from conventional level attractions with the mechanism of either a linear coupling or a dissipation-mediated interaction, and also different from the level repulsion induced by the strong coupling in common polaritons. Our results reveal a new mechanism of level attractions, and open up new roads for exploring the axion polariton with cavity technologies. They have potential applications for quantum information and dark matter research.

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Tunable dynamical magnetoelectric effect in antiferromagnetic topological insulator MnBi2Te4 films

et al. 2021

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Axion was postulated as an elementary particle to solve the strong charge conjugation and parity puzzle, and later axion was also considered to be a possible component of dark matter in the universe. However, the existence of axions in nature has not been confirmed. Interestingly, axions arise out of pseudoscalar fields derived from the Chern–Simons theory in condensed matter physics. In antiferromagnetic insulators, the axion field can become dynamical due to spin-wave excitations and exhibits rich exotic phenomena, such as axion polariton. However, antiferromagnetic dynamical axion insulator has yet been experimentally identified in realistic materials. Very recently, MnBi2Te4 was discovered to be an antiferromagnetic topological insulator with a quantized static axion field protected by inversion symmetry $${\mathcal{P}}$$ P and magnetic-crystalline symmetry $${\mathcal{S}}$$ S . Here, we studied MnBi2Te4 films in which both the $${\mathcal{P}}$$ P and $${\mathcal{S}}$$ S symmetries are spontaneously broken and found that substantially enhanced dynamical magnetoelectric effects could be realized through tuning the thickness of MnBi2Te4 films, temperature, or element substitutions. Our results show that thin films of MnBi2Te4 and related compounds could provide a promising material platform to experimentally study axion electrodynamics.

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Axion Instability and Nonlinear Electromagnetic Effect

Cited by 15 publications

References 39 publications

Axion electrodynamics in topological materials

Axion electrodynamics in topological materials

Unconventional level attraction in cavity axion polariton of antiferromagnetic topological insulator

Tunable dynamical magnetoelectric effect in antiferromagnetic topological insulator MnBi2Te4 films

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