Weyl semimetals are materials where the electronic structure hosts special points known as Weyl nodes, where conduction and valence bands touch. Near these nodes, electrons behave like massless Weyl fermions—particles predicted in high-energy physics but realized in a solid-state context.
These materials exhibit unusual properties due to their topological nature. The Weyl nodes act as monopoles of Berry curvature in momentum space, meaning they are sources or sinks of a quantum geometric field. This leads to phenomena not seen in conventional materials, such as:
- Fermi arcs on the surface—open-ended electronic states connecting Weyl nodes of opposite chirality.
- Chiral anomaly, where an imbalance between left- and right-handed Weyl fermions appears in the presence of electric and magnetic fields.
- Unusual transport behavior, including extremely high mobility and negative magnetoresistance.
Weyl semimetals represent a new phase of quantum matter where topology and symmetry shape the fundamental behavior of electrons, offering insights into both condensed matter and high-energy physics.