Discovery poised to assist detect darkish matter and pave the best way to unravel the universe’s secrets and techniques

Image: (From left) Dr Subhaskar Mandal, Prof Zhang Baile, Prof Chong Yidong.

Researchers led by NTU Singapore have developed a breakthrough method that would lay the foundations for detecting the universe’s “dark matter” and produce scientists nearer than earlier than to uncovering the secrets and techniques of the cosmos.

The issues we are able to see on Earth and in house – seen matter like rocks and stars – make up solely a small portion of the universe, as scientists consider that 85 per cent of matter within the cosmos includes invisible darkish matter. This mysterious substance is alleged to be the invisible glue holding galaxies collectively. Finding it might assist us perceive cosmic phenomena that can not be defined solely by the matter we see.

But proving the existence of darkish matter is a herculean process. As its title suggests, darkish matter is “dark”, that means it doesn’t usually emit or mirror mild, carries no electrical cost and interacts extraordinarily weakly with regular matter, making it undetectable with standard scientific devices.

Dark matter is probably going made up of particles and among the many hypothetical particles proposed for it, a number one candidate is the axion.

Scientists have spent 4 many years in search of axions. One method seeks to show via experiments that current particles in nature, like electrons or mild particles, can behave like theoretical axions. If scientists can observe such behaviour, it will increase the chance that axions could be actual. The findings can then function a springboard to develop a technique for detecting precise axions.

Despite coming shut, the outcomes from the seek for axions stay inconclusive. But scientists led by NTU Singapore have now confirmed that naturally current particles can certainly act like axions.

The researchers’ experiments confirmed that when mild particles, additionally known as photons, journey inside particular crystal buildings that they designed, the photons transfer like theoretical axions.

“The findings from our new crystal structures give us more confidence that we could one day use the crystals to detect real axions,” stated Professor Zhang Baile from NTU’s School of Physical and Mathematical Sciences (SPMS), who led the researchers. “And since axions are promising candidates for dark matter, our research might lay the groundwork for unravelling some of the universe’s greatest mysteries.”

The examine was reported within the scientific journal Science in January 2025.

Illuminating the darkness

The time period darkish matter, coined within the Nineteen Thirties, refers back to the invisible glue hypothesised to forestall spinning galaxies from breaking up, as there may be not sufficient seen matter to account for the gravitational forces holding them collectively. So, darkish matter could possibly be the spine undergirding the universe, which explains how galaxies type and evolve.

The axion is the present main theoretical particle postulated to type darkish matter. Its historical past could be traced to physicists Roberto Peccei and Helen Quinn, who, in 1977, proposed an idea to resolve a particle-physics puzzle. Later, in 1978, physicists Frank Wilczek and Steven Weinberg independently realised the idea steered {that a} new particle existed. Wilczek dubbed this particle the axion, after a laundry detergent model, because it “cleaned up” a theoretical mess in physics.

Axions are believed to have originated from the sudden growth of the universe after it was created in a cosmic occasion known as the Big Bang. If axions are the primary elements of darkish matter, they might be very laborious to detect.

Even so, concept predicts that actual axions can convert into photons in a strong 10 Tesla magnetic area, which is 10 instances stronger than the economic electromagnet used to raise automobiles in scrapyards.

When axions convert into photons, the sunshine particles could be detected utilizing conventional gear to point out that axions exist. However, the conversion is predicted to be extremely inefficient, so the indicators from transformed photons can be weak and simply masked by different indicators. So far, makes an attempt to measure the indicators of transformed photons haven’t succeeded.

Scientists have additionally been making an attempt one other method to discovering axions: displaying that naturally current particles like electrons and photons can mimic axion behaviour after which use the knowledge to develop a technique to detect precise axions.

Researchers have historically centered on making an attempt to show that electrons can act like axions. But previous research have solely proven electrons transferring like axions in two dimensions – comparable to travelling horizontally and vertically – which isn’t adequate since axions transfer and exist in three dimensions.

NTU’s Prof Zhang led his group to deal with this situation by turning to photons. Earlier, his group labored on layered crystal buildings with magnetic properties that may change how mild particles journey and behave in them. The scientists had tried to make use of these crystals to simulate unique particles which might be laborious to search out in nature. But within the course of, the scientists realised that they could have discovered traces of the elusive axions.

Looking additionally at previous theoretical work that hyperlinks axions to magnetic fields oriented in reverse instructions, the researchers hypothesised that photons throughout the crystal might exhibit axion-like behaviour if a crystal’s layers had alternating magnetic properties.

The speculation was confirmed via experiments performed by Prof Zhang’s group in collaboration with Prof Chong Yidong, additionally from SPMS, and different scientists.

In their examine, the researchers used fastidiously designed crystalline geometric buildings manufactured from a man-made garnet crystal known as yttrium iron garnet. This materials has distinctive magnetic and optical properties and is utilized in microwave gadgets inside radar and telecommunication methods.

In their experiments, the group noticed that photons travelled in a single route on the three-dimensional edges of the crystal’s construction – comparable to transferring horizontally, vertically and sideways – with out points like scattering backwards. This behaviour of the photons within the crystal can also be what concept predicts for axions.

To discover actual axions sooner or later, scientists might try to optimise the crystal designs additional and use them in experiments to detect photons transformed from axions underneath excessive circumstances, comparable to sturdy magnetic fields. However, attaining this may require important effort and assets. The group believes that their crystal buildings may have the ability to increase the weak indicators of axion-converted photons, however extra analysis is required to verify this.

Professor Yannis Semertzidis, from the Korea Advanced Institute of Science and Technology in South Korea and who was not concerned within the NTU-led examine, stated that axions are a great, main candidate for darkish matter and sure contribute to a good portion of it.

Prof Semertzidis, who researches on axions, stated that the NTU-led examine is a serious breakthrough, and that the crystal buildings used within the examine set the stage for a “promising alternative” to current strategies for locating axions. He famous that the crystal buildings have inside magnetic fields that “are perfectly suited for axion detection”.

“These crystal structures are expected to become a practical tool for searching axion dark matter in the near future,” added Prof Semertzidis.

 

Paper titled “Photonic axion insulator”, revealed in Science, 10 Jan 2025. DOI: 10.1126/science.adr5234.