Hi Kristjan, I'm working on 3D periodic boundary problem recently. Your code really helps me a lot. I tested your code. It seems working with nanowire leads instead of a periodic repeat in y direction. I changed the leads setting a little as following. A translational symmetry along y direction was added on lead. Then wraparound it with keep=0
lead = kwant.Builder(kwant.TranslationalSymmetry((-a, 0),lat.vec((0, W)))) lead[(lat(0,j) for j in range(W))] = 4*t lead[lat.neighbors(1)] = -t sys.attach_lead(wraparound(lead,keep=0)) sys.attach_lead(wraparound(lead,keep=0).reversed()) It seems working as a periodic boundary condiction. I judge it by settiing all potential to 0 in the scatting region. Then the tramsmittion with energy above 0 should be 1. Without above changes, the transmission at a little positive energy is 0 and the it will jump to 1 at a little higher energy. It implies the transversal energy quantization. I tested the ky under the above flat potential condition. The period of ky is 2Pi instead of 2Pi/L. I don't know why. Maybe some expert can explain it. Anyway, I'm just a newbie with kwant and trying to solve some bulk problem with it. I'm not sure about the above opinion. Let's discuss and figure out how it works in peroidic boundary condiction. -- Mingkai Li
