A Weyl fermion is a type of elementary particle that was first proposed by the physicist Hermann Weyl in 1929. It is named after him in recognition of his contribution to theoretical physics. Weyl fermions have unique properties and behave differently from other types of fermions, such as electrons or quarks.
Weyl fermions are massless particles that obey the Weyl equation, which is a relativistic wave equation that describes their behavior. Unlike other fermions, such as electrons, which have both left-handed and right-handed components, Weyl fermions come in two distinct types: left-handed Weyl fermions and right-handed Weyl fermions. Left-handed Weyl fermions have a left-handed spin orientation, meaning that their spin is aligned with their momentum, while right-handed Weyl fermions have a right-handed spin orientation.
An important property of Weyl fermions is their chiral nature. Chirality refers to the asymmetry between left and right. In the context of Weyl fermions, chirality is associated with the helicity of the particle, which is the projection of its spin along its direction of motion. Left-handed Weyl fermions have left-handed chirality, while right-handed Weyl fermions have right-handed chirality.
One of the remarkable features of Weyl fermions is that they exhibit a phenomenon called the chiral anomaly. The chiral anomaly is a quantum mechanical effect that leads to the violation of the conservation of chiral charge, which is associated with the difference between the number of left-handed and right-handed particles. This anomaly has profound implications in the behavior of Weyl fermions in the presence of external electromagnetic fields.
Weyl fermions have attracted significant interest in recent years due to their potential implications in condensed matter physics and high-energy physics. In condensed matter systems, Weyl fermions can emerge as quasiparticles in certain exotic materials called Weyl semimetals. These materials exhibit interesting electronic properties, such as the existence of Fermi arcs and the generation of exotic transport phenomena. In high-energy physics, Weyl fermions have been proposed as possible building blocks for new physics beyond the Standard Model, such as theories of quantum gravity or extensions of the Standard Model.
In summary, Weyl fermions are massless elementary particles with chiral properties, exhibiting distinct left-handed and right-handed components. They have unique features, including chiral anomaly and potential applications in condensed matter physics and high-energy physics.