Dear Gabriel,

Try this:

from matplotlib import pyplot as plt
from matplotlib import backends
import kwant

t = 1 # hopping parameter
L=5
lat = kwant.lattice.general([(1,0),(0,1)],[(0,0),(.5,0)], norbs=1)
a, b = lat.sublattices

syst = kwant.Builder()

# Scattering region
for i in range(L):
syst[a(i, 0)] = 0
syst[b(i, 0)] = 0

syst[kwant.builder.HoppingKind((0, 0), a, b)] = -t
syst[kwant.builder.HoppingKind((1, 0), a, b)] = -t

#syst[lat.neighbors()]=-t
kwant.plot(syst)
plt.show()

# leaft lead (lead 1)

lat_lead1 = kwant.lattice.general([(1,0),(0,1)],[(0,0)], norbs=1).sublattices[0]
sym_lead1 = kwant.TranslationalSymmetry((-1, 0))

syst[lat_lead1(-1,0)] = 0
syst[lat_lead1(-1,0),lat_lead1(0,0)] = -t

syst[lat_lead1(5,0)] = 0
syst[lat_lead1(5,0),b(4,0)] = -t

lead1 = kwant.Builder(sym_lead1)

lead1[lat_lead1(0,0)] = 0
lead1[lat_lead1.neighbors()] = -t

syst.attach_lead(lead1)
syst.attach_lead(lead1.reversed())
kwant.plot(syst)

# In[77]:

import numpy as np
sysf=syst.finalized()

# In[78]:

Trans=[]
energies=np.linspace(-1.99,1.99,100)
for energy in energies:
SM=kwant.smatrix(sysf,energy)
T=SM.transmission(0,1)
Trans.append(T)

# In[79]:

from matplotlib import pyplot
pyplot.plot(energies,Trans)
pyplot.show()

Regards,

On Wed, Jun 7, 2023 at 10:41 PM Gabriel Garcia <gqgarcia99@gmail.com> wrote:

Dear Adel,

Thanks for answering me. I saw the FAQ and I try to reproduce for my case, but unfortunately didn't work. I changed the lead command:

# Lead a direita (lead 1)
lat_lead1 = kwant.lattice.square(C)
sym_lead1 = kwant.TranslationalSymmetry((-C, 0))

lead1 = kwant.Builder(sym_lead1)

lead1[(lat_lead1(0, 0))] = 0
lead1[lat_lead1(0,0), lat_lead1(1,0)] = -t

syst[(a(0,0), lat_lead1(-1,0))] = -1

syst.attach_lead(lead1)

kwant.plot(syst)
plt.show()

---------------------------------------------------------------------------
KeyError Traceback (most recent call last)
<ipython-input-8-df1e018f6b56> in <module>
8 lead1[lat_lead1(0,0), lat_lead1(1,0)] = -t
9
---> 10 syst[(a(0,0), lat_lead1(-1,0))] = -1
11
12 syst.attach_lead(lead1)

~\anaconda3\lib\site-packages\kwant\builder.py in __setitem__(self, key, value)
1160 func = (self._set_site if isinstance(sh, Site)
1161 else self._set_hopping)
-> 1162 func(sh, value)
1163
1164 def _del_site(self, site):

~\anaconda3\lib\site-packages\kwant\builder.py in _set_hopping(self, hopping, value)
1136 # of identical sites.
1137 a2 = a = self.H[a][0]
-> 1138 b2 = b = self.H[b][0]
1139 else:
1140 b2, a2 = sym.to_fd(b, a)

KeyError: Site(kwant.lattice.Monatomic([[2.0, 0.0], [0.0, 2.0]], [0.0, 0.0], '', None), array([-1, 0]))

If anyone can help me, i appreciate. Thaks.

Gabriel Garcia