Until now, physics has distinguished between fermions and bosons, but now there are indications of a third type of particle
At first glance, our world appears to be enormously complex. However, according to the laws of particle physics, it is strictly ordered. According to this, there are only two classes of particles, the matter particles and the force particles. All known matter in the universe is made up of the former. These include, in particular, electrons and quarks, which make up the protons and neutrons in atomic nuclei. The force particles, on the other hand, include light particles or photons. However, two physicists, Zhiyuan Wang from the Max Planck Institute of Quantum Optics in Garching and Kaden Hazzard from Rice University in Houston, have now discovered that a third class of particles can exist: the so-called paraparticles.
The two particle classes of matter and force particles differ on a fundamental theoretical level in that they obey opposing statistics. -Matter particles are also called fermions, while force particles are called bosons," says Zhiyuan Wang. In the case of matter particles, two of them can never be in the same state in the same place. Ultimately, this leads to the stability of matter, otherwise everything would collapse.
The opposite is true for force particles: they can condense at will. For example, it is possible to concentrate a gigantic number of light particles in powerful laser pulses. In the 1950s, the idea emerged that there could also be so-called para-particles, which obey different statistical rules. -After some time, however, it turned out that the paraparticles devised at the time were ultimately nothing more than a hidden combination of fermions and bosons," explains Wang. Their physical properties ultimately did not differ from the already known particle classes.
Particles with completely new properties
However, with their new theory, Wang and Hazzard are now postulating a class of particles that should exhibit completely new behavior. -Our paraparticles are based on a completely different mathematical structure and therefore have fundamentally different properties to fermions and bosons," says Wang. The two researchers are not initially focusing on new types of matter particles such as electrons, but rather on so-called quasiparticles in solids.
Such quasiparticles are formed, for example, when two electrons in a superconductor bind together to form a pair. There are many types of such quasiparticles, which are being researched in solid-state physics in particular.
States of matter that contain paraparticles could occur both in two-dimensional, atomically thin layered structures and in bulk materials. However, theories still need to be developed as to which materials could actually contain paraparticles.
-Paraticles have exotic properties that do not occur in ordinary particles," explains Wang. Thanks to the mathematical tools he developed together with Hazzard, these new properties can be studied in detail. These additional particle properties can be visualized as an arrow pointing in different directions, depending on the inner quantum state of the paraticle.
Possible applications in quantum communication
Thanks to the so-called parastatistics that these particles obey, various applications are conceivable. If two of these particles are spatially interchanged, their properties change together - even without them coming into direct contact. This could be used for a special form of quantum cryptography. Wang says: "Two parties with paraparticles could communicate with each other simply by exchanging positions, without meeting or exchanging messages, and without leaving a trace that a third party could spy on. Thanks to their very special quantum properties, paraparticles could also be of interest for the construction of quantum computers.
It has also been speculated that paraparticles could be behind the dark matter that makes up a large part of the mass in the universe. So far, particle physicists and astrophysicists have been desperately searching for any clue as to what this dark matter could consist of. Perhaps they have been looking in completely the wrong place because they didn’t have the paraparticles on their screen? -We have already had inquiries from a few researchers in the field of dark matter, but I have to admit that I hardly know anything about this area myself," says Wang. I still consider assumptions in this direction to be very risky until we can show, at least theoretically, that elementary para-particles can also exist - so far, the theory has only formulated para-particles as quasi-particles.
A chance discovery in mathematics
The story of how the new theory came about is itself a little exotic and did not follow a fixed plan. -During the Covid pandemic in 2021, I was bored at home working on a strange mathematical problem that at first glance had nothing to do with physics at all, - says the researcher. -I then found an unusual solution to this problem, and it was only when I interpreted it physically that I came up with the idea of paraparticles." It then took another three years to complete the theory.
In any case, it will be interesting to see whether and in what form paratellites are found. The 2016 Nobel Prize in Physics was awarded for research into topological properties in solids. These are also closely linked to the particle statistics of electrons and quasiparticles. Para-particles could provide an exciting addition to the palette.
Dirk Eidemüller
