Fermions with cubic and quartic spectrum
T. T. Heikkilä *, G. E. Volovik*+ 1)
* Low Temperature Laboratory, Aalto University, School of Science and Technology, FI-00076 AALTO, Finland
+Landau Institute for Theoretical Physics RAS, 119334 Moscow, Russia
Abstract
We study exotic fermions with spectrum . Such
spectrum emerges in the vicinity of the Fermi point with multiple
topological charge N, if special symmetry is obeyed. When this
symmetry is violated, the multiple Fermi point typically splits into
N elementary Fermi points - Dirac points with N=1 and spectrum
.