Dark matter is a hypothetical substance that outweighs regular matter – which makes stars, planets, and everything we can see and touch – by five to one. But we don’t know what it is. One hypothesis, with some astronomical backing, is that it is made of extremely light particles known as axions. Researchers have now developed a new method to look for these axions by making something like an axion in the lab.
Axions have some very specific properties in how they interact with other particles and even light. Dark matter is a bit of a misnomer because it should be invisible matter, since we cannot see it. However, axions have an extremely weak but specific interaction with light, which can potentially be used to find them.
We’ve discovered something that’s actually axion-like, which has never been done before.
Dr Doddy Marsh
In the new work, researchers did not find axions, but they were able to create a quasiparticle – an interaction that behaves like a particle – and this quasiparticle behaved like an axion. They called it DAQ, dynamical axion quasiparticle. This was done by Jian-Xiang Qiu, a graduate researcher in Su-Yang Xu’s lab at Harvard.
The DAQ was found in a manganese, bismuth, and tellurium material (MnBi2Te4), which has some very intriguing magnetic properties. The finding would be exciting in itself, but this quasiparticle could be used to find the real deal.
“We’ve discovered a new type of a new type of quasiparticle. We’ve discovered something that’s actually axion-like, which has never been done before,” Dr David J. “Doddy” Marsh, from King’s College London, told IFLScience.
A crucial discovery of the last century is the duality of waves and particles. Light can be seen as waves and particles, but also as matter. An electron is both a particle and a wave. The axion, too. And it would be a wave with a very long wavelength and very low frequency. One can picture them as a field spreading through all the space rather than little clumps of stuff floating about.
“If dark matter is a wave, then it’s just oscillating up and down, so the way you try and detect it is you look for that oscillation, just like we looked for the oscillation of the axial quasiparticle,” Dr Doddy Marsh explained.
“It’s like if you’re trying to find a radio station. Imagine your radio station is 96.7 FM, and then you want to find it. You have to tune your car radio to 96.7. But if you show up somewhere, like in a new country, and you don’t know what radio stations are going to be good, you start tuning your radio and you might go past something that’s good.”
We can’t look up a good radio station frequency for axions on a website, but this is where the DAQ comes in. The DAQ has a specific oscillation at 44 gigahertz, but this can be tuned to different frequencies using a strong magnetic field. The axion dark matter field would interact with the DAQ when their frequencies match, creating resonance.
This method would test a range of possible frequencies (and masses) that have not been explored yet. Dark matter might not be made of axions; it might be made up of Weakly Interacting Massive Particles (WIMPs), or it may be something else entirely. But if it is axions, Marsh believes that we are years away from discovering them.
“There are lots of experiments that are happening or going to happen in the next 10 to 20 years. If axion dark matter exists, if it’s, you know, a big part of the dark matter… if it’s 50 to 90 percent or something, of the dark matter, will find it,” Dr Marsh told IFLScience.
A paper describing the work is published in the journal Nature.
Source Link: Tunable Dark Matter Detector Developed With Never-Before-Seen Quasiparticle
