a cylindrical bundle of wires where the space between them can vary
Tune the plasma frequency by varying the spacing between the wires. Illustration by A. Millar.


The new VR research environment AxionDM: Detecting Axion Dark Matter In The Sky And In The Lab is a multidisciplinary collaboration between cosmologists and particle, condensed matter and theoretical physicists in order to explore new techniques for searching for dark matter axions. Local participants in the grant include Stefano Bonetti, Jan Conrad, Jón Gudmundsson, Matthew Lawson, David Marsh, Alex Millar, Hiranya Peiris, Keir Rogers, and Frank Wilczek. The project will recruit postdoctoral researchers with expertise in axion phenomenology, computational condensed matter physics, and experimental condensed matter physics.

"I'm happy to see this grant awarded to Stockholm University, it will certainly raise the profile of Stockholm in the dark matter community. Axions are a leading candidate for dark matter, and therefore if they exist they could make up the 80% of the matter in the universe that we have not yet identified" -- OKC postdoctoral researcher Matthew Lawson.

Three research areas will be the focus of this new environment:

  • Development of an axion-plasmon haloscope which uses tunable metamaterials
  • Exploring astronomical signals from axion dark matter
  • Identifying a set of materials that are sensitive to the coupling between collective excitations of particles and axions

The axion-plasmon haloscope is a completely new proposal for axion detection, led by postdocs Matthew Lawson and Alexander Millar along with Nobel laureate Frank Wilczek, who was one of the first to envision the axion. This instrument, which consists of wire metamaterials designed to detect oscillations from axions inside a strong magnetic field, will be unique in that it can be tuned by varying the spacing between wires. A subscale technology testbed will be constructed and tested with candidate plasmas, paving the way for a full-scale experiment.

Not only is the axion a great and interesting dark matter candidate, but also the leading explanation for one of the puzzling symmetries we see in nature, that the Strong nuclear force is the same regardless of the direction of the flow of time. As more and more serious experimental efforts are being realised, it's important to make sure that we look for the axion in varied and innovative ways. -- OKC postdoctoral researcher Alex Millar.

Astronomical observations may be able to detect axions via their effects on the Lyman-alpha forest power spectrum or using radio signals from clumps of gravitationally bound axions. A Bayesian emulator for the Lyman-alpha forest that incorporates sophisticated reionization simulations will be built and used to place limits on ultralight axion dark matter. Axion dark matter clumps affected by astrophysical objects may produce radio emission. These signals will be characterized and their detectability investigated.

The power of this grant is in its funding of interdisciplinary collaboration. The research environment will bring together not just particle theorists, but also experimentalists, cosmologists, astronomers and machine learning expertise. As a cosmologist myself, I’m looking forward to searching for the imprint of axion-like particles in the early Universe using light from very distant but very bright galaxies called quasars. -- OKC postdoctoral researcher Keir Rogers.

Condensed matter physics has shown that collective excitations of particles in systems can themselves have particle properties. If these collective excitations couple to axions then they may be be used to detect them. Research efforts will analytically compute the coupling between different classes of collective excitations and the axion in order to identify candidate materials. THz time-domain spectroscopy will be used to study the materials and promising materials will be further characterized in terms of other properties.

Hiranya Peiris, who will coordinate the research environment, said “VR’s new investment illustrates the power of a bottom-up approach to developing innovative research programmes – in this case the project was conceived largely within the fertile environment at a local OKC journal club. It is also pleasing to see the recognition of an interdisciplinary approach that combines the leadership and expertise of researchers at a variety of career stages.”