Every discovered fundamental particle in the universe has an antiparticle, that antiparticle has the same mass but opposite charge. If it ever happened for two particles to meet, they would destroy each other releasing a certain amount of energy. There is an ongoing theory for a long time that says there is exception to this rule. Exceptions would be those particles that are in the same time their own antiparticles. There is recently strong evidence discovered by the research team from University of California and Stanford University – naming it the “angel particle”.
The theory comes from physicist named Ettore Majorana who highlighted the gap in the fermion family of particles in 1937. Electrons, protons, neutrinos, neutrons and quarks are fermions, which means they all have their matching antiparticles. But Majorana calculated that there should exist particles which are in the same time their own antiparticles.
Neutrons and neutrinos had the best chance to be these Majorana fermions as they don’t have charge, but since then, anti-neurons have been discovered. There are still some questions concerning neutrinos, and currently there are ongoing experiments that should resolve if neutrinos are their own antiparticles. But according to the difficulty of these experiments, results and answers are probably more than decade away.
Currently, the most likely way to find Majorama fermions is by looking for things called “quasiparticles.” As the name says, these really not really natural particles per-se. They emerge out of collective behavior of the electrons and only have some properties of particles. The best explanation is from the Encyclopaedia Britannica. They are described as bubbles that appear in the drinks. Those bubbles arise out of the “collective behavior” of the chemicals in the drink and have measurable properties like objects, but they are not really independent objects.
Just like bubbles, quasiparticles will occur only inside of very specific conditions, and they can only be considered to be Majorama fermions if they show all the right properties. UC and Stanford scientists said they have found the evidence that clearly points to the existence of hypothetical fermions.
One of the senior authors of the research paper, Shoucheng Zhang sad: “Our team predicted exactly where to find the Majorana fermion and what to look for as its ‘smoking gun’ experimental signature,” adding that “This discovery concludes one of the most intensive searches in fundamental physics, which spanned exactly 80 years.”
To find these quasiparticles, scientists very carefully built a specific environment made up of thin films of two quantum materials stacked on top of one another. The result was a superconducting topological insulator that allowed electrons to move fast along the edges of the surface of the material. They added a bit of magnetic material that made the electrons flow in one direction along one edge, and back along the other edge.
Sweeping a magnet over the material slowed down the electrons, made them stop and switch direction. Quasiparticles then began to arise in pairs, traveling along the same path as the electrons. But there was one difference, when they stopped and turned around, they did it in steps exactly half as high as the electrons.That happened because each quasiparticle is only a half of a particle as one out of each quasiparticle pair is lost along the way – and that was what researches were looking for.
Zhang proposed discovery to be called the “angel particle” after the novel Angels and Demons, in which is mentioned a bomb powered by the matter and antimatter together.