Chiral electronic network within skyrmionic lattice on topological insulator surfaces

We consider a proximity effect between Dirac surface states of a topological insulator and the skyrmion phase of an insulating magnet. A single skyrmion results in the surface states having a chiral gapless mode confined to the perimeter of the skyrmion. For the lattice of skyrmions, the tunneling coupling between confined states leads to the formation of low-energy bands delocalized across the whole system. We show that the structure of these bands can be investigated with the help of the phenomenological chiral network model with a kagome lattice geometry. While the network model by itself can be in a chiral Floquet phase unattainable without external periodic driving, we show how to use a procedure known as band reconstruction to obtain the low-energy bands of the electrons on the surface of the topological insulator for which there is no external driving. We conclude that band reconstruction is essential for the broad class of network models recently introduced to describe the electronic properties of different nanostructures.