Weyl semimetals

Definition

Weyl semimetals are a class of materials that possess unique electronic properties characterized by the presence of Weyl nodes, which are points in momentum space where the conduction and valence bands meet. These materials are significant in the study of quantum phenomena and have been shown to exhibit high mobility of charge carriers, making them of interest for applications in electronics and photonics.

5 Must Know Facts For Your Next Test

1. Weyl semimetals can be classified into type-I and type-II based on the energy dispersion around the Weyl nodes, affecting their electronic properties.
2. They exhibit exotic phenomena such as the chiral anomaly, where charge conservation can be violated under certain conditions, influencing their conductivity.
3. The observation of Fermi arcs, which are surface states connecting Weyl nodes in momentum space, highlights the topological nature of these materials.
4. Weyl semimetals have potential applications in spintronics due to their unique spin textures and the ability to manipulate spin currents.
5. Terahertz spectroscopy is an effective tool for characterizing Weyl semimetals, allowing researchers to probe their electronic dynamics and identify Weyl nodes.

Review Questions

• What are Weyl nodes, and how do they influence the electronic properties of Weyl semimetals?
  • Weyl nodes are points in momentum space where the conduction and valence bands touch, leading to unique electronic properties such as high mobility and the presence of Fermi arcs. The location and characteristics of these nodes determine how charge carriers behave within the material. This gives Weyl semimetals distinctive features that set them apart from conventional materials, making them interesting for advanced applications.
• Discuss the significance of chiral anomaly in Weyl semimetals and its implications for electronic transport.
  • The chiral anomaly in Weyl semimetals occurs when the conservation of charge is violated due to the nontrivial topology of their band structure. This phenomenon can lead to increased conductivity under certain conditions, affecting how electrical currents flow within these materials. Understanding this anomaly is crucial for leveraging the unique transport properties of Weyl semimetals in next-generation electronic devices.
• Evaluate how terahertz spectroscopy can be used to probe Weyl semimetals and what information it reveals about their electronic dynamics.
  • Terahertz spectroscopy is a powerful technique for investigating Weyl semimetals as it allows for direct probing of their electronic dynamics and band structure. This method can help identify Weyl nodes and observe features such as Fermi arcs through the analysis of absorption and transmission spectra. The ability to examine these materials under varying temperatures and magnetic fields further enhances our understanding of their quantum behavior and potential applications in advanced technologies.

Related terms

Topological insulators: Materials that behave as insulators in their interior but conduct electricity on their surface, with surface states that are protected by time-reversal symmetry.

Dirac cones: The conical dispersion relation seen in materials such as graphene, indicating massless charge carriers and resulting in high electron mobility.

Chirality: A property of Weyl fermions in Weyl semimetals that describes the handedness of the particles, leading to unique transport phenomena.