The existence of a new form of matter is proved: excitonium

Since the 1960s, theoretical physicists have assumed the existence of an unusual superconducting material, but scientists could prove its existence with the help of quantum mechanics only 50 years later.

Researchers from the University of Illinois announced the discovery of a new form of matter, which was called “excitonium” (Latin excitonium). This material consists of particles like bosons, which allow the matter to exhibit the properties of a superfluid, superconductor and even an insulating electronic crystal.

Professor Peter Abbamont and his team worked together with physicists from the University of California, Berkeley and the University of Amsterdam. Their goal was to prove the existence and study the properties of the mysterious type of matter, which was theoretically described more than 50 years ago and has so far been the subject of heated debate. The work of scientists is published in the journal Science.

Secrets of quantum mechanics

The excitonium is a condensate consisting of excitons, which in turn are quasiparticles, which are a bound state of an electron and a so-called “hole”, another quasiparticle. Such a clever quantum mechanical synthesis is possible due to the fact that in semiconductors, electrons on the edge of one energy level of the atom are able to move to another energy level upon excitation, leaving a hole behind them. One can imagine this quasiparticle as an opening acting as a positively charged particle, which tends to attract an electron that has escaped from it (having a negative charge).

In order to prove the existence of excitons, the team of physicists studied crystals covered with titanium dielcogenide (1T-TiSe2). For greater reliability, the experiment was reproduced five times. Until now, exciton studies have remained a field of theories and assumptions largely because scientists simply did not have suitable technical equipment. But now, armed with highly sensitive instruments, physicists were able to measure for the first time the joint excitation of low-energy boson particles (electron-hole pairs), however weak their impulses were.

Meaning of discovery

In an official press release, Abbamont states that the new discovery has literally “cosmic significance”. Since the theoretical physicist Bert Halperin of Harvard coined the term “excitonium” in the 1960s, other physicists have tried to prove or disprove his existence. They discussed whether the substance behaves like an ideal conductor, a superfluid liquid or an insulating material, leading to very convincing arguments in the arguments. In the late 1970s, many experimenters published works in which they announced the discovery of a long-awaited substance, but the results of their studies were not the final proof – a similar pattern could have been created by a conventional structural phase transition.

Now, when the existence of excitonium is proven, the scientists will take a more detailed study of its properties. As a superconductor and superfluid material, it can be used to further improve existing technologies. In addition, the very fact of its discovery is proof of the possibility of using quantum mechanics for applied purposes and, perhaps, thanks to this research, our understanding of physics will in the near future move to a qualitatively new level.