準粒子を用いたダークマター探索の新手法を発見（Hunting a Basic Building Block of the Universe）

2026-01-05 アルゴンヌ国立研究所（ANL）

Schematic diagram showing both the magnetism and the conductive behavior on the surface of manganese bismuth telluride. (Image by D. Nevola/Brookhaven National Laboratory.)

＜関連情報＞

• https://www.anl.gov/article/hunting-a-basic-building-block-of-the-universe
• https://www.nature.com/articles/s41586-025-08862-x
• https://arxiv.org/abs/2411.03432

2D MnBi2Te4におけるアクシオン準粒子の観察 Observation of the axion quasiparticle in 2D MnBi2Te4

Jian-Xiang Qiu,Barun Ghosh,Jan Schütte-Engel,Tiema Qian,Michael Smith,Yueh-Ting Yao,Junyeong Ahn,Yu-Fei Liu,Anyuan Gao,Christian Tzschaschel,Houchen Li,Ioannis Petrides,Damien Bérubé,Thao Dinh,Tianye Huang,Olivia Liebman,Emily M. Been,Joanna M. Blawat,Kenji Watanabe,Takashi Taniguchi,Kin Chung Fong,Hsin Lin,Peter P. Orth,Prineha Narang,… Su-Yang Xu
Nature  Published:16 April 2025
DOI:https://doi.org/10.1038/s41586-025-08862-x

Abstract

The axion is a hypothetical fundamental particle that is conjectured to correspond to the coherent oscillation of the θ field in quantum chromodynamics^1,2. Its existence would solve multiple fundamental questions, including the strong CP problem of quantum chromodynamics and dark matter, but the axion has never been detected. Electrodynamics of condensed-matter systems can also give rise to a similar θ, so far studied as a static, quantized value to characterize the topology of materials^3,4,5. Coherent oscillation of θ in condensed matter has been proposed to lead to physics directly analogous to the high-energy axion particle—the dynamical axion quasiparticle (DAQ)^{6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23}. Here we report the observation of the DAQ in MnBi₂Te₄. By combining a two-dimensional electronic device with ultrafast pump–probe optics, we observe a coherent oscillation of θ at about 44 gigahertz, which is uniquely induced by its out-of-phase antiferromagnetic magnon. This represents direct evidence for the presence of the DAQ, which in two-dimensional MnBi₂Te₄ is found to arise from the magnon-induced coherent modulation of the Berry curvature. The DAQ also has implications in light–matter interaction and coherent antiferromagnetic spintronics²⁴, as it might lead to axion polaritons and electric control of ultrafast spin polarization^{6,15,16,17,18,19,20}. Finally, the DAQ could be used to detect axion particles^21,22,23. We estimate the detection frequency range and sensitivity in the millielectronvolt regime, which has so far been poorly explored.

誘導および自発アキシオン散乱の理論 A theory of Stimulated and Spontaneous Axion Scattering

M. Smith, Kartiek Agarwal, Ivar Martin
arXiv  Submitted on 5 Nov 2024
DOI:https://doi.org/10.48550/arXiv.2411.03432

Abstract

We present a theory for nonlinear, resonant excitation of dynamical axions by counter-propagating electromagnetic waves in materials that break both P and T symmetries. We show that dynamical axions can mediate an exponential growth in the amplitude of the lower frequency (Stokes) beam. We also discuss spontaneous generation of a counter-propagating Stokes mode, enabled by resonant amplification of quantum and thermal fluctuations in the presence of a single pump laser. Remarkably, the amplification can be orders of magnitude larger than that obtained via stimulated Brillouin and Raman scattering processes, and can be modulated with the application of external magnetic fields, making stimulated axion scattering promising for optoelectronics applications.