In recent years many three-dimensional crystals have been discovered whose low energy electronic properties are described by the Dirac or Weyl equations for relativistic fermions. This lead…
In recent years many three-dimensional crystals have been discovered whose low energy electronic properties are described by the Dirac or Weyl equations for relativistic fermions. This leads to many unusual physical properties and potentially to new applications. This review explains the theory behind these developments, their material realizations, and the current experimental status.