Scientists Spotted ‘Massless’ Electrons Moving in 4 Dimensions
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Scientists in Japan have isolated an important type of electron for further study.
Dirac electrons develop in certain conditions where cone-shaped openings appear in solid matter.
A new paper detailing their isolation adds more dimension to the subject.
In new research published in the peer-reviewed journal Materials Advances, physicists detail how they were able to examine an electron behavior that’s never been isolated before. They were looking at Dirac electrons, which are found in special conditions.
But in the past, they’ve always been in the mix with other types of electrons, making them difficult to study. Now, finally isolating them has let physicists study their unique properties: becoming effectively weightless and able to travel at photon-like speeds, up to the speed of light itself.
All it took was 12,000 times the average barometric pressure of Earth and a special kind of spin.
There are some big terms to define here. Dirac electrons have a key role in a relatively recent discovery called topological materials. These are compounds that conduct electricity only on their outer surfaces—their interiors continue to act as insulators. Think of it like a rubber ball with electrical wires wrapped around it, except somehow the entire thing is made from the same one material. Understandably, this discovery won the Nobel Prize in 2016, the Institute of Electrical and Electronics Engineers (IEEE) explains.
In solid matter physics (including the study of conductors and quantum behaviors), scientists pick apart all the different ways unusual particles behave under unusual conditions. Earth, overall, is quite predictable in terms of how minerals and substances work, but those predictable patterns can become a lot more interesting if we mess with the parameters enough. Radiation, for example, happens naturally, and was greatly accelerated in lab settings to make nuclear power plants. Quantum phenomena—like particles being able to travel almost instantaneously across distances—also require special attention in the lab.
But it's not easy to study behavior on a quantum scale. To do that, scientists create conditions like extreme cold and pressure. This greatly slows down even the most elusive particles, and changes the very nature of how solid materials behave. Pathways for electrons grow, constrict, multiply, disappear—anything goes, depending on the material. In superconducting materials, electrons travel unimpeded by any resistance at all. In Dirac materials, according to Science Alert, “[T]he overlap of atoms puts some of their electrons into a strange space that allow[s] them to jump around materials with excellent energy efficiency.”
The issue is that, while scientists have been looking for and detecting Dirac-tivity for many years now—English physicist Paul Dirac first described it in 1928—it’s very hard to isolate and observe these electrons up close instead of in a noisy group picture, on top of already being hard to observe for their quantum-ness alone. But after studying the existing body of work and doing some new research of their own, scientists from Ehime University, Toho University, and Hokkaido University (all in Japan) realized they could use a specific material that best highlighted the different spin of the Dirac electrons.
That made it easier to pick out these electrons for further study through a process called electron spin resonance—unpaired electrons are proverbially shaken loose from the material, like keeping beach balls in the air above a waving tarp. In solid matter, this is done using spectroscopy, which is the same field that can help scientists identify stars and black holes. Only those beach ball-like free electrons respond to the spectroscopy.
Finally finding a way to isolate the illusive Dirac electrons wasn’t the only things scientist managed to discover in this study, however. For one, it was unexpected that the crystalline polymer critical to this experiment would be three dimensional instead of a single-layer nanosheet of something like graphene. Looking through you, as the Beatles famously did, is a lot easier when you're just one particle thick. But it served its purpose rather nicely at its wider size.
For another, mapping the Dirac electrons this way and making them more uniform in terms of observed spin, let the researchers make further observations about how they behave. When the temperature of the material passes above 100 Kelvin, or a chilly -280 Fahrenheit, the conical Dirac shapeways really open up. Since the polymer isn't as thin, the cones are more defined and closer to the three dimensions that scientists hope for in order to use these materials in real life applications.
Only time will tell what those applications will be.
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