Dear all,
I make AGNR in Kwant and introduce the defect in both the scattering region and lead.
When plotting the bandstructure of the lead there is a straight line that comes at E=0.
I am confused that there is some error in the code or not. Please help
Thanking You
code-
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import kwant
import numpy as np
import matplotlib.pyplot as plt
pi = np.pi
a = 1
d = 1.42;
a1 = d*np.sqrt(3);
lat = kwant.lattice.general(
[[a1, 0], [a1/2, a1*np.sqrt(3)/2]],[[0, 0], [0, a1/np.sqrt(3)]]
)
a,b = lat.sublattices
def set_pub(): # for plotting the figures
plt.rcParams.update({
"font.weight": "bold", # bold fonts
"font.size":18,
#"tick.labelsize": 15, # large tick labels
"lines.linewidth": 2, # thick lines
"lines.color": "k", # black lines
"grid.color": "0.5", # gray gridlines
"grid.linestyle": "-", # solid gridlines
"grid.linewidth": 0.5, # thin gridlines
"xtick.major.size":10,
"xtick.minor.size":5,
"ytick.major.size":10,
"ytick.minor.size":5,
"savefig.dpi": 600, # higher resolution output.
})
def make_sys(w,l):
def rect(pos):
x,y = pos
return -w*a1<x<w*a1 and -l*a1<y<l*a1
model1 = kwant.Builder()
model1[lat.shape(rect,(1,1))] = 0
model1[lat.neighbors()] = 2.46
return model1
def lead_join(model1,w):
def lead_shape(pos):
x, y = pos
return -w*a1<x<w*a1
Num = 8*(a1*np.sqrt(3)/2)
sym = kwant.TranslationalSymmetry([0,Num])
lead = kwant.Builder(sym)
lead[lat.shape(lead_shape, (1,1))] = 0
lead[lat.neighbors()] = 2.46
model1.attach_lead(lead)
model1.attach_lead(lead.reversed())
return model1,lead
def defect(model1,lead):
def delet_lead(pos, shift = +a1*np.sqrt(3)):
x, y = pos
z=x**2+(y-shift)**2
return z<(a1)**2
def delet_str(pos, shift = a1*np.sqrt(3)):
x, y = pos
z = x**2 + (y-shift)**2
return z<(a1)**2#z<(2*a1)**2
del model1[lat.shape(delet_str, (1,1))]
del lead[lat.shape(delet_lead, (2,2))]
kwant.plot(model1)
set_pub()
plt.rc('axes', linewidth = 2.0)
plt.show()
return model1
def plot_bandstructure(flead, momenta):
bands = kwant.physics.Bands(flead)
energies = [bands(k) for k in momenta]
band_gap = 100
for k in momenta:
for band in bands(k):
if(band <0):
#Lower than fermi band
min_band=band
else:
max_band=band
if(max_band-min_band<band_gap):
band_gap=max_band-min_band
break
print("Gap Energy= " + str(band_gap) +" ev ")
kwant.plotter.bands(flead) # bandstructure of lead
plt.ylim([-3,3])
set_pub()
plt.xlabel("K $(\AA^{-1})$",fontweight='bold')
plt.ylabel("Energy (eV)",fontweight='bold')
plt.show()
return band_gap
def main():
w = 5
l = 8
sys = make_sys(w,l)
syst,lead = lead_join(sys,w)
syst = defect(syst,lead)
fsys = syst.finalized()
momenta = [-pi + 0.02 * pi * i for i in range(101)]
Band_Gap = plot_bandstructure(lead.finalized(), momenta)
if __name__ == '__main__':
main()