Dear sir, 
I understand what you have said.  But how can I maintain translation symmetry ?because my system is 3D and for plotting current I access the sites of 3D system using list(sys.sites) and plot the current for 2D slice. Please suggest me.

Best Regards
Naveen Yadav
Research Scholar
Department of Physics & Astrophysics
University of Delhi
New Delhi-110007

On Thu, May 7, 2020, 19:06 Abbout Adel <abbout.adel@gmail.com> wrote:
Dear Naveen,

What you get is what is expected. You do not have translational symmetry.
Rewrite your code by keeping only two dimensions and you will see why.

I hope this helps,
Adel


On Thu, May 7, 2020 at 12:52 PM Naveen Yadav <naveengunwal72@gmail.com> wrote:
Dear KWANT Developers,
I am trying to plot the current density. The procedure is straightforward. I have attached leads to the scattering region (leads have same onsite and hopping as of the scattering region) as
sys[(lat(z,y,x) for z in range(H) for y in range(W)for x in range(L))]=onsite
sys[kwant.builder.HoppingKind((1, 0, 0), lat, lat)] = hoppingz
sys[kwant.builder.HoppingKind((0, 1, 0), lat, lat)] = hoppingy
sys[kwant.builder.HoppingKind((0, 0, 1), lat, lat)] = hoppingx

lead=kwant.Builder(kwant.TranslationalSymmetry((1,0,0)))
lead[(lat(z,y,x)  for z in range(H) for y in range(W)for x in range(L))]=onsite
lead[kwant.builder.HoppingKind((1, 0, 0), lat, lat)] = hoppingz
lead[kwant.builder.HoppingKind((0, 1, 0), lat, lat)] = hoppingy
lead[kwant.builder.HoppingKind((0, 0, 1), lat, lat)] = hoppingx
sys.attach_lead(lead, add_cells=80)
sys.attach_lead(lead.reversed())
image.png
As you can see from the plot there is a discontinuity in the plot at (W=20).  Why it is so even if the scattering region and leads have same onsite and hopping and there is translation symmetry throughout ?

--
Best Regards,
Naveen Yadav
Research Scholar
Department of Physics & Astrophysics
University Of Delhi
New Delhi-110007


--
Abbout Adel