Hi all. I would like to know how to compute Hall conductance in a honeycomb lattice using Kwant. In my attempt, I started with the construction of the honeycomb lattice: import kwantimport matplotlib.pyplot as pltimport numpyfrom cmath import expfrom kwant.digest import gauss lat = kwant.lattice.honeycomb()sys = kwant.Builder() def rectangle(pos): x, y = pos return 0 < x < 40 and 0 < y < 20 sys[lat.shape(rectangle, (1, 1))] = 0sys[lat.neighbors()] = -1 sym = kwant.TranslationalSymmetry((-1, 0))sym.add_site_family(lat.sublattices[0], other_vectors=[(-1, 2)])sym.add_site_family(lat.sublattices[1], other_vectors=[(-1, 2)]) lead = kwant.Builder(sym) def lead_shape(pos): x, y = pos return 0 < y < 20 lead[lat.shape(lead_shape, (-1,1))] = 4lead[lat.neighbors()] = -1 sys.attach_lead(lead)sys.attach_lead(lead.reversed()) My questions are: How to attach another pair of leads at 13 < x < 15 and 23 < x < 25 with y = 10 and y =0? I tried # For the 2nd Lead sym2 = kwant.TranslationalSymmetry((-1, 0)) sym2.add_site_family(lat.sublattices[0], other_vectors=[(-1, 2)]) sym2.add_site_family(lat.sublattices[1], other_vectors=[(-1, 2)]) lead2 = kwant.Builder(sym) def lead2_shape(pos2): x, y = pos2 return 13 < x < 15, 10 < y < 10 lead[lat.shape(lead2_shape, (1,1))] = 4 lead[lat.neighbors()] = -1 sys.attach_lead(lead2) sys.attach_lead(lead2.reversed()) but nothing works. Also How to calculate hall conductance from these leads (assuming hopping is by Peierls substitution where t is replaced by an exponential)? I am very new to the kwant program, as this is for an undergraduate research.Regards, James