Module weyl 

Weyl Semimetal Materials

Weyl semimetals are topological quantum materials where conduction and valence bands touch at discrete points (Weyl nodes) in momentum space. These nodes act as monopoles of Berry curvature, leading to exotic phenomena like the chiral anomaly and giant anomalous Hall effect.

Physics Background

Weyl Nodes:

• Point degeneracies with linear dispersion E(k) = ℏv_F |k|
• Characterized by chirality (monopole charge): ±1
• Protected by topology (cannot be gapped without breaking symmetry)

Key Phenomena:

1. Chiral Anomaly: Parallel E and B fields cause charge pumping between nodes
2. Fermi Arc Surface States: Open arcs connecting Weyl nodes of opposite chirality
3. Anomalous Hall Effect: Large intrinsic Hall conductivity from Berry curvature
4. Negative Magnetoresistance: From chiral anomaly

Material Classes:

• Type-I: Weyl nodes with point-like Fermi surface
• Type-II: Tilted Weyl cones with finite Fermi surface
• Magnetic: Time-reversal broken, minimum 2 Weyl nodes
• Non-magnetic: Inversion broken, minimum 4 Weyl nodes

Key References

• S.-Y. Xu et al., “Discovery of a Weyl fermion semimetal and topological Fermi arcs”, Science 349, 613 (2015) - TaAs
• B. Q. Lv et al., “Experimental Discovery of Weyl Semimetal TaAs”, Phys. Rev. X 5, 031013 (2015)
• N. P. Armitage et al., “Weyl and Dirac semimetals in three-dimensional solids”, Rev. Mod. Phys. 90, 015001 (2018)
• E. Liu et al., “Giant anomalous Hall effect in a ferromagnetic kagome-lattice semimetal”, Nat. Phys. 14, 1125 (2018) - Co₃Sn₂S₂

Structs

WeylSemimetal

Weyl semimetal material properties

Enums

MagneticState

Magnetic state

WeylType

Weyl semimetal classification