Traces of an Exotic Particle That Eluded Physicists For 80 Years

Physicists used a scanning tunneling microscope to capture an image of the neutral charge signature of the Majorana fermion at the end of the wire.

(Image credit: Yazdani Lab/Princeton University)

A mysterious particle made of both matter and antimatter has eluded physicists for 80 years, but now, researchers have spotted traces of it.

Physicists think each particle has its own antiparticle with the same mass but an opposite charge. But the new particle, called a Majorana (pronounced mai-yor-ah-na) fermion, acts as its own antimatter partner and has a neutral charge. The particle is puzzling, because physicists know that when matter and antimatter collide, they annihilate each other. In the 1930s, physicist Ettore Majorana proposed that a particle existed that was made of both matter and antimatter; even so, physicists could not find any trace of the particle — until now.

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Catching a glimpse of this sneaky particle was not easy. Ali Yazdani, a professor of physics at Princeton University, and colleagues used a giant, two-story microscope to zero in on a tiny iron wire only a few atoms long. They placed the wire on top of a chunk of lead and cooled it to minus 458 degrees Fahrenheit (minus 272 degrees Celsius), or near absolute zero. [The 9 Biggest Unsolved Mysteries in Physics]

Using the huge microscope, the researchers detected neutral signals coming from the ends of the wire — the key signature of Majorana fermions that decades of research and calculations have predicted. This detection method is different from that used to elucidate other exotic particles, like the Higgs boson, which was detected inside the Large Hadron Collider (LHC), the world's largest atom smasher. The LHC smashes atoms together at near light speed and creates particles in a vacuum.

It took Yazdani and the team two years to get the balance between the magnetic field and the superconductive state just right, but the Majorana fermions finally emerged at the ends of the wire. The researchers could pinpoint the Majorana particles because their matter and antimatter components make them electrically neutral. The giant scanning tunneling microscope, which can image surfaces at the atomic level, captured images of the neutral electric signals.

So physicists have been on the lookout for a way to make quantum bits more stable. Majorana fermions are surprisingly stable for being made of two elements that are supposed to annihilate each other. The matter and antimatter in a Majorana fermion also gives it a neutral charge so it barely interacts with its environment. These properties could make the Majorana fermion a much more stable way to encode quantum information, since their superposition state would be more resistant to collapse, physicists say.

Kelly Dickerson is a staff writer for Live Science and Space.com. She regularly writes about physics, astronomy and environmental issues, as well as general science topics. Kelly is working on a Master of Arts degree at the City University of New York Graduate School of Journalism, and has a Bachelor of Science degree and Bachelor of Arts degree from Berry College. Kelly was a competitive swimmer for 13 years, and dabbles in skimboarding and long-distance running.