Dear Javad tavakoli,

I think you need to see the kwant documentation carefully. From the first look at your script I can notice the following statements.

So let us start with the symmetry and the shape of your lead.

First you have used kwant.TranslationalSymmetry((0,0,1)) which means you are going along the z direction where -2pi/z<Kz<+2pi/z.

Second you have defined the lead shape as a finite shape since you have included 10 <= z < 25

def lead_shape(pos):
x,y,z = pos
return 0 <= x < a and 0 <= y < b and 10 <= z < 25

I guess if you omit 10 <= z < 25 from def lead_shape(pos) you would get something meaningful.

Try to fix this problem and let me know if working or not

Best wishes

Adel

Le ven. 18 juin 2021 à 22:33, tavakkolidjawad <tavakkolidjawad@ut.ac.ir> a écrit :

Dear all

In the following code I have defined a three-dimensional structure.
The geometry of the lead and the scattering region are the same, but the lead is not ploted as I expected.
I expected the lead to have a cubic structure.
What is the problem with my code?

Thanks

Javad tavakoli

############################################################################

############################################################################

import kwant

lat = kwant.lattice.general([(0, 0.5, 0.5), (0.5, 0, 0.5), (0.5, 0.5, 0)],
[(0, 0, 10), (0.25, 0.25, 10.25)], name=['a1', 'a2'])
a1, a2 = lat.sublattices

def make_system(a=10, b=10, c=30):

syst = kwant.Builder()

def cuboid_shape(pos):
x, y, z = pos
return 0 <= x < a and 0 <= y < b and 0 <= z < 10

syst[a1.shape(cuboid_shape, (0, 0, 0))] = 1
syst[a2.shape(cuboid_shape, (0, 0, 0))] = 1
syst[lat.neighbors()] = 1

def lead_shape(pos):
x,y,z = pos
return 0 <= x < a and 0 <= y < b and 10 <= z < 25

lead = kwant.Builder(kwant.TranslationalSymmetry((0,0,1)))
lead[a1.shape(lead_shape, (0, 0, 10))] = 1
lead[a2.shape(lead_shape, (0, 0, 10))] = 1
lead[lat.neighbors()] = 1

syst.attach_lead(lead)
syst.attach_lead(lead.reversed())

return syst , lead

def main():

syst,lead= make_system()

kwant.plot(syst)

syst,lead = make_system(a=1.1, b=1.1, c=1.1)

syst.attach_lead(lead)

if __name__ == '__main__':
main()

###########################################################################