Most of the scientists and researchers believe that our universe was formed because of big bang happened around 13.7 billion years ago. The explosion created equal amounts of matter and antimatter.
Everything around us is made of matter. A particle is quality of matter, with no specific size restriction. Physicists can define particles to be electrons while astronomers can define it to be stars in the space. It all depends on the field and theory under study.
In 1928, an English theoretical physicist made a strange prediction that every fundamental particle has an antiparticle. For those who don’t know, antiparticle is exactly like particle but contains opposite charge. When antiparticle and particle meet, they annihilate, releasing a vast amount of energy.
In 1932, an American physicist Car David Anderson discovered the first antimatter particle, Positron (which is electron’s opposite), and since then antimatter became the inseparable part of science.
Four years later, in 1937, another genius physicist from Italy, Ettore Majorana, made a whole new prediction – for a type of particles called fermions (or Majorana fermion) that includes electron, neutron, proton, quark and neutrino, there should be particles having their own antiparticles.
He suggested that the neutral spin-1/2 particles could be described by a Majorana equation, which proves that they are identical to their antiparticle.
Recently, in July 2017, a team of Stanford scientists discovered the first evidence of Majorana particle in several experiments conducted on exotic material. They have done these experiments along with University of California, under the supervision of Professor Kang Wang, while the theoretical predictions came from Shoucheng Zhang’s group.
The researchers have named their discover the “Angel Particle” after the best selling thriller book ‘Angels and Demons’ by Dan Brown. The book includes creating a time bomb from a combination of matter and antimatter. However, in quantum world, Majorana particles represent only angles, no demons.
The concept of ‘particle that is its own antiparticle’ is not new. Scientists from all over the world have been trying to prove its existence for the last 80 years.
In order to actually know that fermions exists, the researchers first need to discover quasiparticles – particle-like excitations, which arise out the behavior of superconducting materials that are capable of conducting electricity with 100% efficiency.
Quasiparticles aren’t found in nature, and they fit in the mathematical model that defines actual Majorana fermions. In the last couple of years, researchers have conducted several experiments involving superconducting nanowires, and they have found some promising results (of Majorana fermion’s existence).
However, the quasiparticles were sticked to one specific location, instead of propagating in space and time. This made it difficult to identify whether other effects were responsible for the signals that scientists observed.
Experiment and Technical Details
In condensed matter systems, Majorana fermions could be realized as quasiparticles of topological states of quantum matter, for instance, n=5/2 quantum Hall state, two-dimensional px + ipy spinless superconductors, Moore Read type states in fractional quantum Hall effect, ferromagnetic atomic chains on a superconductor and strong spin-orbit coupling semiconductor heterostructures.
In this experiment, scientists stacked 2 thin films inside a cold vacuum chamber, of which one was a magnetic insulator (on the bottom) and another was a superconductor (on the top), and they passed electric current through them.
The film on the bottom could conduct current along its edges or surface, not through the middle. Therefore, both films together made a superconducting topological insulator. Now the electrons can move along edges of 2 material’s surface, without any resistance.
The small quantity of magnetic material added on insulator enabled the electrons to flow in one direction along one surface’s edge and the opposite direction along the opposite surface’s edge.
The next thing scientists did is, they slightly moved a magnet (a conventional magnet) over the stack, in order to control the electrons flow. This allowed them to stop, slow the speed or switch the direction of electrons. Although changes were not so smooth, they happened in abrupt steps.
Illustration of 2 thin quantum materials with electron flow direction
At a particular point, Majorana quasiparticles evolved in pairs out of thin superconducting film. Like electrons, they moved along the edges of insulator. One quasiparticles in each pair was diverted out the path, and this made it easy for scientists to calculate the flow of individual quasiparticles. They observed that quasiparticles stopped, slowed and altered direction in steps, exactly half as high as the electrons.
This is the evidence scientists had been looking for. These quasiparticles are the result of material’s excitations that act like Majorana fermions. They are created in an artificial way with special materials. They don’t exist in the universe (what we know so far).
This specific type of Majorana particle is called Chiral fermion because it flows in one direction in one dimensional path.
Chiral Majorana edge modes in the quantum anomalous Hall insulator–superconductor structure
Although the search for the fermion seems more intellectual than practical, in the far future, it could have real life implications for developing robust quantum computers.
A single Majorana fermion is half a subatomic particle, therefore one qubit could be stored in 2 separate Majorana fermions. Since the information is stored in two different fermions, the probability of losing the information is significantly reduced.