I am using two leads (left and right) where their widths are larger the
scattering region. For instance, the sites of the scattering region are between
the vertical interval y1 <= y <= y2, so its width is W = y2-y1 +1. The
sites of the leads are of course between 0 <= y <= W_lead. So, W < W_lead. The
problem is that attach_lead doesn't work, unless one includes sites in the
scattering region for 0<= y < y1, y2<y<=W_lead. Thus I did not define hoppings
for those zones, however attach_lead() imposes spurious horizontal hoppings at
the frontiers, otherwise it gives an error message. it seems that attach_lead
needs to connect the whole frontier of any lead. Is there any way for avoiding
these spurious horizontal hoppings ?.
