Nontrivial gapless states at the stacking faults of weak topological insulators

<p>This code is used to study the topological properties of weak topological insulators in the presence of a stacking fault. Each WTI is made by a stack of zigzag ribbons stacked on top of each other in the z direction. There are two types of WTIs taken into consideration. One has a topological ribbon and a insulating spacer in each unit cell (two layers per unit cell). The other one has one topological layer and two spacers in each unit cell (three layers per unit cell).</p>