Predicted Particle Defies Fundamental Law of Universe

November 27, 2015 | Joanne Kennell

Abstract artistic impression of a particle system
Photo credit: Andreas Wetterberg/Flickr (CC BY-SA 2.0)

And it exists in a “material universe.”

An international team of scientists from Princeton University have predicted the existence of a new type of particle. If they’re correct, type-II Weyl fermion would defy some universal rules of physics.

The name Weyl may sound familiar to you.  Earlier this year in July, researchers finally found the Weyl fermion that was predicted to exist 85 years ago by Hermann Weyl.  Wait, if the Weyl fermion was predicted 85 years ago, how was type-II not predicted also?  The researchers believe that Weyl missed the particles existence because it violates a fundamental law known as Lorentz symmetry, which is a strict rule-set applied to quantum field theory.  As it turns out, Lorentz symmetry does not apply in materials where this new type of fermion is found.

Scientists believe that this new particle will be found in condensed matter solid — a class of crystals nicknamed a “material universe.”  Just as electrons are the elementary particles in our universe, Bloch electrons (also known as quasiparticles) are the elementary particles of a solid.  The crystal is, in essence, its own little "universe" and can contain all of the particles found in the our universe.

SEE ALSO: Physicists Finally Find “Glueball” Particle Made of Pure Force

Researchers noticed something very strange about the behaviour of one of the metallic crystal material known as tungsten ditelluride — it was acting as either a near perfect conductor or an insulator depending on the direction of the magnetic field.

This is strange because most metals either become insulators when in the presence of a magnetic field, and metallic crystals containing Weyl fermions become super-efficient conductors.  Neither of these were happening with tungsten ditelluride.  This led researchers to predict that the strange behaviour had to be the result of the existence of a new particle, the type-II Weyl fermion.

Luckily, these crystals are easy to study because they can be grown in laboratories, so experiments can begin quickly to prove the existence of the fermion. This particle, if found, may provide important applications to technology.  If type-II Weyl is anything like its relative, Weyl, it may be capable of conducting current extremely fast, leading to more efficient electronics.

"Even more intriguing is the perspective of finding more 'elementary' particles in other condensed matter systems," the researchers say. "What kind of other particles can be hidden in the infinite variety of material universes? The large variety of emergent fermions in these materials has only begun to be unraveled."

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