Weyl fermions from crystal symmetry

DIPC Seminars

Juan Luis Mañes
Donostia International Physics Center
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Weyl fermions from crystal symmetry We consider the existence of massles Dirac (Weyl) fermions around points of symmetry in the Brillouin zone of 3D crystals with negligible spin-orbit interaction. We use group theory to show that this is possible, but only for a reduced number of space groups and points of symmetry. Moreover, we show that for a handful of space groups the existence of Weyl fermions is not only possible but unavoidable, irrespective of the concrete crystal structure. Thus our results can be used to look for Weyl fermions in a specific class of systems, namely that of nonmagnetic 3D crystals with sufficiently weak spin-orbit coupling. A simple tight-binding model is used to illustrate some of the issues.