Download Dirac and Weyl fermions in condensed matter systems: an introduction

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3D Weyl fermions: Weyl semimetals
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2-band degeneracy point in k-space with linear dispersions.
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NO symmetry needed to protect this degeneracy.
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Such Weyl nodes must appear in pairs of opposite chirality.
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Weyl nodes of opposite chirality can be mutually gapped out
if they meet in k-space. Break inversion and/or TR symmetry
to separate them. [Burkov&Balents, PhysRevLett'11]
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Weyl nodes are difficult to locate
(usually not on high symmetry lines)
Example: TaAs.
no inversion symmetry,
12 pairs of Weyl nodes.
2015/12/[email protected]