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Physicists Report a Particle That Is Both Matter and Its Own Antimatter Counterpart

majorana fermion2

Image credit: Ilya Dorzdov, Yazdani Lab, Princeton University. The peaks at the end of an iron wire indicate an absence of magnetism characteristic of a long-sought particle.

It is surprisingly known to most physics students that all basic particles are characteristic of being particles as well as waves. However, for the first time in history, physicists have discovered something much unusual: a particle is matter, but it is also antimatter.

Since the 1930s, the subatomic speck, also called as the “Majorana fermion”, has been theoretically known, but never actually observed before. According to Professor Ali Yazdani of PrincetonUniversity, the fermion was expected to appear at the edge of certain materials, from which point, it had been observed to be set at each end of a single-atom-thick wire.

In 1928, antimatter was predicted by scientists, but only in 1932 it was confirmed. Like ordinary matter, antimatter is kind of particles with the same mass, but opposite in charge. It was Ettore Majorana who found in 1937 that a particle could be both matter as well as antimatter, and to his surprise, such particle was much stable in this state. Unfortunately, in 1938, Mojorana went missing because of some mysterious circumstances, thus bringing the end to his remarkable career expected in future.

Majorana’s theory seemed unbelievable, because in general once matter and antimatter come across each other, both of them would be destroyed, so that a lot of energy would be released in such process. But in Majorana’s mathematical calculation, his claim looked like an unassailable one. When matter and antimatter properties were combined, it would allow the particle to remain neutral; therefore, putting gravity aside, it could seldom interact with the matter around it. It has been speculated that neutrinos would actually be Majorana fermions.

In the article published in Science, Yazdani provided some information about the production of an iron wire located on an ultrapuresuperconducting lead crystal. At 1K (-272°C) with help of spectroscopic imaging techniques, it was revealed that the ends of the wire were in zero energy states. Such situation was long expected if Majoranas had generated at these ends. In 2001, the appearance of Majoranas at the ends of superconducting wires was predicted.

Yazdani and his colleagues confirmed in their article that unlike what would happen if Majoranas had been made in high-speed energy accelerators, theirs were quite clean and could be removed from any spurious particles. In 2012, the possible Majoranas was observed, but Yazdani was not sure about it. As Yazdani said, the microscope demonstrated that this signal lived just at the edge, which was not necessarily regarded as the case for the previous experiment. However it was really the key signature, without it, such signal could stay there for many other reasons.

It is hoped that materials combined with the Majorana would release more about the quantum information in a much stable way, thus giving strong support to the possibility of quantum computing.

Ilya Dorzdov, Yazdani Lab, Princeton University. A scanning-tunneling microscope creates a magnetic field to map the presence of a neutral signal that indicates the presence of Majorana fermions at the ends of an iron wire on a lead crystal.

Journal reference: Nadj-Perge, Stevan, et al. “Observation of Majorana fermions in ferromagnetic atomic chains on a superconductor.” arXiv preprint arXiv:1410.0682 (2014).

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