Fermions follow a certain set of rules in quantum mechanics. They include quarks, electrons, protons, and others. Weyl fermions, which remain hypothetical, are odd in that they appear to be lacking in any mass whatsoever, and that is what the team’s models appear to have conjured up.
"The massless property of Weyl fermions comes from the fact that their energy doesn't depend on mass, which means they bear a resemblance to photons," co-author Sarah Grefe, a graduate student of physics at Rice University, told IFLScience. Essentially, these fermions still have mass, but "they just effectively act like they don't have one."
Now, Weyl fermions are thought to exist in certain materials that conduct electrical currents. Materials known as topological conductors, for example, are suspected of carrying electricity through their interior, thanks to the presence of these Weyl fermions.
The first solid evidence of their existence dates back to 2015, when three independent groups of physicists spotted them for the first time in a semimetal named tantalum arsenide. This was based on somewhat indirect evidence of a “formation” known as a Fermi arc.
What the team headed by Rice University has now found is additional model evidence for a new type of quantum material featuring these Weyl fermions. But wait – what’s with the “Kondo” part?
The so-called Kondo effect explains that electrons within a magnetic metal are sometimes scattered due to a chemical impurity. This ends up altering the material’s ability to resist electrical current, depending on what its temperature is.
It appears that, according to the team’s models, the Kondo effect is the progenitor of the Weyl fermions they observed. Thus, the quantum material their work points to has been dubbed a “Weyl-Kondo semimetal”.
Again, this material does not yet exist. With this work, however, it soon might – and who knows what bonkers properties it’ll have when it does emerge?