Dear all,

I am trying to make an armchair nanoribbon as following:

import kwant
from math import sqrt
import matplotlib.pyplot as plt
import tinyarray
import numpy as np
import math
import cmath
#import scipy.linalg as la
import matplotlib
d=1.42;
a1=d*math.sqrt(3);

#on-site energy...................................................
t=-2.7;

latt = kwant.lattice.general([(0,a1),(a1*math.sqrt(3)/2,a1*0.5)],
                             [(-d/2,a1/2),(d/2,a1/2)])
a,b = latt.sublattices
syst= kwant.Builder()

def rectangle(pos):
    x, y = pos
    return -2.4*a1<x<2.4*a1 and -3*d<y<3*d

syst[latt.shape(rectangle, (1,1))]=0

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

ax=kwant.plot(syst);

sym = kwant.TranslationalSymmetry(latt.vec((-1,2)))

lead = kwant.Builder(sym)

def lead_shape(pos):
    x, y = pos
    return  -3*d<y<3*d

lead[latt.shape(lead_shape, (1,1))]=0

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

syst.attach_lead(lead,add_cells=0)
syst.attach_lead(lead.reversed(),add_cells=0)
ax=kwant.plot(syst);

 It is ok and I have no problem with it. I have problem when I tried to make a defect (like making a hole) on the scattering rigion and also lead.

I used a same method for making a defect on both scattering region and lead but the results are not same.

Would you please help me what is a problem. Would you please let me know if symmetry vector (sym = kwant.TranslationalSymmetry(latt.vec((-1,2))))

used is ok?

Best wishes,

Sajad