Physicists have discovered a strange new state of matter in the form of a highly ordered crystal of subatomic particles. The new state of matter, called a “bonded boson insulator,” could lead to the discovery of many new types of exotic materials made of condensed matter, according to the researchers, who explain their findings in a study published May 11 in the journal Nature. Sciences.
Subatomic particles can be separated into two classes: fermions and bosons. The primary differences between the two are how they rotate and how they interact with each other.
Fermions, such as electrons and protons, are often thought of as the building blocks of matter because they make up atoms, and are characterized by their half-correct spin. Two identical fermions cannot occupy the same space at the same time.
Bosons, on the other hand, carry force — like photons, or packets of light — and are thought to be the glue of the universe, holding together basic forces of nature. These particles contain an integer spin, and multiple bosons can exist in the same place at the same time.
Related: Physicists create a new state of matter from a quantum soup of magnetically exotic particles
“Bosons can occupy the same energy level; fermions don’t like staying together,” said the study’s lead author. Qinhao Jina condensed matter physicist at the University of California, Santa Barbara, said in A statement. “Together, these behaviors build the universe as we know it.”
But there is a case in which two fermions can turn into a boson: If a negatively charged electron is secured to a positively charged “hole” in a different fermion, it forms a boson particle known as an “exciton”.
To see how the excitons interact with each other, the researchers placed a lattice layer of tungsten disulfide on top of a similar lattice of tungsten diselenide in an overlapping pattern called a moire. Next, they shone a powerful beam of light through the gratings — a method known as “pump-probe spectroscopy.” These conditions pushed the excitons together until they became so densely packed that they could no longer move, creating a new, symmetrically charged, neutrally charged crystal state—a correlated boson insulator.
“Traditionally, people have put most of their effort into understanding what happens when you put many fermions together,” said Jin. “The main thrust of our work is that we made a new material from the interacting bosons.”
The researchers said this is the first time that this new state of matter has been created in a “real” matter system, as opposed to synthetic systems, providing new insight into the behavior of the bosons. What’s more, the methods the team used to discover this new state of matter could help scientists create additional new types of bosonic matter.
“We know that some materials have very strange properties,” Jin said. “One of the goals of condensed matter physics is to understand why it has such rich properties and to find ways to make these behaviors appear more reliably.”