• Axion quasiparticles have been observed for the first time in a two-dimensional quantum material (MnBi2Te4).
• The discovery provides a new detection strategy for fundamental axions, a leading dark matter candidate.
• The research may lead to the development of new axion dark matter detectors and advancements in ultrafast antiferromagnetic spintronics.

A team of physicists led by Jianxiang Qiu at Harvard University has successfully detected axion quasiparticles within a two-dimensional quantum material composed of manganese bismuth telluride (MnBi2Te4). This material, a topological antiferromagnet, exhibits insulating properties in its bulk while conducting electricity on its surface. The experiment involved using ultrafast pump-probe spectroscopy to observe coherent oscillations indicative of the axion quasiparticle. This breakthrough not only provides a novel approach for detecting dark matter but also opens doors for advancements in materials science and spintronics.

• What: Detection of axion quasiparticles in a two-dimensional quantum material (MnBi2Te4) using ultrafast pump-probe spectroscopy.
• Who: Jianxiang Qiu (Harvard University) and colleagues.
• When: Research published in Nature, reported May 2, 2025.
• Where: Harvard University (research location).

The detection of axion quasiparticles in MnBi2Te4 marks a significant advancement in the search for dark matter. The use of a topological antiferromagnet allows for the creation of quasiparticles that mimic the behavior of fundamental axions, providing a tangible way to study their properties. The potential to hybridize these quasiparticles with photons to create axion-polaritons opens up new avenues for research in ultrafast antiferromagnetic spintronics. Overcoming the technical barrier of growing high-quality crystals of MnBi2Te4 will be crucial for maximizing the sensitivity of future detectors.

This is uniquely enabled by the out-of-phase magnon in this topological material. Such coherent oscillations are the smoking-gun evidence for the axion quasiparticle and it is the combination of topology and magnetism in MnBi2Te4 that gives rise to it.

The observation of axion quasiparticles in a topological antiferromagnet represents a promising step forward in the quest to understand dark matter and develop new technologies. While challenges remain in material engineering and detector development, the potential applications in dark matter detection and spintronics make this a significant area of ongoing research.