Dimensional crossover in topological matter: Evolution of the multiple Dirac point in the layered system to the flat band on the surface
T. T. Heikkilä*, G. E. Volovik *+
*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 consider the dimensional crossover in the topological matter,
which involves the transformation of different types of topologically
protected zeroes in the fermionic spectrum. In the considered case, the
multiple Dirac (Fermi) point in quasi 2-dimensional system evolves into the
flat band on the surface of the 3-dimensional system when the number of
atomic layers increases. This is accompanied by formation of the spiral nodal
lines in the bulk. We also discuss the topological quantum phase transition
at which the surface flat band shrinks and changes its chirality, while the
nodal spiral changes its helicity.