Type-II Weyl semimetals
By Alexey A. Soluyanov, Dominik Gresch, Zhijun Wang, Quansheng Wu, Matthias Troyer, X. Dai, A. Bernevig. Nature, 2015
2,230 citations recorded by the source corpus.
Fermions—elementary particles such as electrons—are classified as Dirac, Majorana or Weyl. Majorana and Weyl fermions had not been observed experimentally until the recent discovery of condensed matter systems such as topological superconductors and semimetals, in which they arise as low-energy excitations. Here we propose the existence of a previously overlooked type of Weyl fermion that emerges at the boundary between electron and hole pockets in a new phase of matter. This particle was missed by Weyl because it breaks the stringent Lorentz symmetry in high-energy physics. Lorentz invariance, however, is not present in condensed matter physics, and by generalizing the Dirac equation, we find the new type of Weyl fermion. In particular, whereas Weyl semimetals—materials hosting Weyl fermions—were previously thought to have standard Weyl points with a point-like Fermi surface (which we refer to as type-I), we discover a type-II Weyl point, which is still a protected crossing, but appears at the contact of electron and hole pockets in type-II Weyl semimetals. We predict that WTe2 is an example of a topological semimetal hosting the new particle as a low-energy excitation around such a type-II Weyl point. The existence of type-II Weyl points in WTe2 means that many of its physical properties are very different to those of standard Weyl semimetals with point-like Fermi surfaces.
Subfields: Atomic and Molecular Physics, and Optics, Materials Chemistry
View Paper: https://www.semanticscholar.org/paper/d924e0ad307c2ce986f802be204b7df86af23bc0
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In Atomic and Molecular Physics, and Optics
- Ashvin Vishwanath
- Nathan Goldman
- N. P. Armitage
- Claudia Felser
- E. Mele
- D. Vanderbilt
- J. Moore
- Bogdan Andrei Bernevig
In Materials Chemistry
- Ashvin Vishwanath
- Claudia Felser
- N. P. Armitage
- E. Mele
- J. Moore
- Binghai Yan
- D. Vanderbilt
- Bogdan Andrei Bernevig
Citations in the corpus
- Weyl and Dirac semimetals in three-dimensional solids (2017, background): “Such a term is forbidden by Lorentz symmetry for the Weyl Hamiltonian in vacuum but it can generically appear in a linearized long wavelength theory near an isolated twofold band cross- 9 ing in a crystal (Soluyanov et al., 2015; Wan et al., 2011).”
- Quantized circular photogalvanic effect in Weyl semimetals (2016, background): “If the tilting is strong enough to create a type II node [53, 54], the surface of allowed transitions encompasses only a fraction”
- Topological Semimetals from First Principles (2018, background): “These attributes, in combination with their topological characteristics, have led to the identification of a growing number of different TSM families, which include Dirac and Weyl semimetals (4, 5, 6, 7), nodal line semimetals (8, 9, 10), type-I and type-II semimetals (11), multifold fermion semimet”