Dear Kwant Community
I am new in Kwant and trying to compute a simple 1-D system's conductance.
However something strange confuse me that when the Fermi energy gets adjusted
into some specific range (like (0,1) or (-1,2)), the Jupyter says: "shape
mismatch: value array of shape (2,2) could not be broadcast to indexing result
of shape (2,4)".
More mystical, if I tuned it to other range (like(-5,5)) or considered 2-D
condition，the error would disappear.
I don't know what happend QAQ , could anyone please give me some explanation?
This is my code:
import kwant
# For plotting
from matplotlib import pyplot
import numpy as np
sigma_0=np.array([[1,0],[0,1]])
sigma_x=np.array([[0,1],[1,0]])
sigma_y=np.array([[0,-1j],[1j,0]])
sigma_z=np.array([[1,0],[0,-1]])
U=4
def make_system(a=1, t=1.0, L=5):
lat = kwant.lattice.chain(a,norbs=2)
syst = kwant.Builder()
#### Define the scattering region. ####
for x in range (L):
syst[(lat(x))] = (2*t+U)*sigma_0
syst[lat.neighbors()] = -t*sigma_0
#### Define and attach the leads. ####
lead0 = kwant.Builder(kwant.TranslationalSymmetry([-a]))
lead0[(lat(0))] = 2*t*sigma_0
lead0[lat.neighbors()] = -t*sigma_0
lead1 = kwant.Builder(kwant.TranslationalSymmetry([a]))
lead1[(lat(0))] = 2*t*sigma_0
lead1[lat.neighbors()] = -t*sigma_0
syst.attach_lead(lead0)
syst.attach_lead(lead1)
return syst
#================================================================
def plot_conductance(sys,energies):
data=[]
for energy in energies:
#<-Fermi energy
smatrix=kwant.smatrix(sys,energy)
data.append(smatrix.transmission(1,0))
plt.figure()
plt.plot(energies, data)
plt.xlabel("energy")
plt.ylabel("conductance [e^2/h]")
plt.show()
def main():
syst=make_system()
kwant.plot(syst)
sys=syst.finalized()
Es = np.linspace(-1,1, 100)
#<-Fermi energy
plot_conductance(sys,Es)
if __name__ == '__main__':
main()
I guess it occuers because zero energy may causes some singular conditions, but
I badly don't know why XD.
Thanks for reading.
Sincerely,
Intpret
