Re: [Kwant] armchair nanoribbon with defect

4 Nov 2019


      Dear nafise,
Good day, it seem that you have problem with symmetry.
To some up you have to fix the following issues:
1. define the lattice.general correctly
2. provide larger limit along x for the rectangle, so we might avoid
isolated atoms(unconnected)
3. chose the symmetry as Num = 8*(a1*sqrt(3)/2) and then use  sym =
kwant.TranslationalSymmetry([0, Num])
4. shift the origin of y direction in your delet function by
(y-a1*sqrt(3))**2 intead of y**2
5. the boundary in lead_shape is for x not y. If we use y the code will bug
(infinity system)
Please, you have one thing left to do. kindly make sure that the lead is
100% armchair, perhaps Mrs Josefe or About would be for a help.
I have plotted the bands for the lead, it seems armchair but I still do
not  muster 100% the source code of  kwant.plotter.bands. Please check this
pont.
See the code with explanation
Happy kwanting

Best Adel

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*sqrt(3);

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

latt = kwant.lattice.general([[a1, 0], [a1/2, a1*sqrt(3)/2]],  # lattice
vectors
                                 [[0, 0], [0, a1/sqrt(3)]])  # Coordinates
of the sites
a, b = latt.sublattices

syst= kwant.Builder()


## you have to provide quite big boundaries to avoid isolated atoms so
abs(x)=4*a1
def rectangle(pos):
    x, y = pos
    z=x**2+y**2
    return -4*a1 a écrit :
...
Dear Joseph
At first thank you for kwant team. My problem for zigzag nanoribbon with
defect (hole) was solved with your help. Now I have a bit problem with
armchair nanoribbon. I have changed zigzag nanoribbon according to making
the armchair nanoribbon. It is OK when we have no defect on the system but
when I try to make hole on the scattering region and leads I have a
problem. The shape of holes  on  the scattering region and leads are not
same. My code is as the following. That is very king of you if you help me
where is the problem.
Thanks In advance for your help.
Beat wishes,
Nafise
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
    z=x**2+y**2
    return -2.4*a1
syst[latt.shape(rectangle,(1,1))]=0
def delet(pos):
    x, y = pos
    z=x**2+y**2
    return  z<(2*a1)**2
del syst[latt.shape(delet, (1,1))]
#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((-2,4)))
lead = kwant.Builder(sym)
def lead_shape(pos):
    x, y = pos
    return  -5*d
lead[latt.shape(lead_shape, (1,1))]=0
def delet_lead(pos):
    x, y = pos
    z=x**2+y**2
    return  z<(2*a1)**2
del lead[latt.shape(delet_lead, (1,1))]
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);

Re: [Kwant] armchair nanoribbon with defect

Adel Belayadi