Hi Kwant Users !
I was trying to plot the band structure of the ssh model with linearly
varying chemical potential (\mu*x). But it is showing error that "*Expecting
an arraylike object or a scalar*" while adding this potential term. Can
anyone please tell where I am making mistake and how to rectify it ?
_____________________________________
Code is attached below :-
import kwant
import numpy as np
import math
##
import matplotlib
#matplotlib.use('Agg')
##
# For plotting
from matplotlib import pyplot as plt
# For matrix support
import tinyarray
I2 = tinyarray.array([[1,0], [0,1]])
Sx = tinyarray.array([[0,1], [1,0]])
Sy = tinyarray.array([[0,-1j], [1j,0]])
Sz = tinyarray.array([[1,0], [0,-1]])
Sp = tinyarray.array([[0,2], [0,0]])
Sm = tinyarray.array([[0,0], [2,0]])
def create_system(length=10):
t1 = 0.5 ; t2 = 1.0 ;
def Onsite(site):
(x, ) = site.pos
potential = x
return x
# system building
lat = kwant.lattice.square(a=1, norbs=2)
syst = kwant.Builder()
# central scattering region
syst[(lat(x, 0) for x in range(length))] = t1*Sx
syst[lat.neighbors()] = (t2*Sx - 1j*t2*Sy)/2
# add leads
sym = kwant.TranslationalSymmetry((-1, 0))
lead_left = kwant.Builder(sym)
lead_left[lat(0, 0)] = t1*Sx + Onsite*I2
lead_left[lat.neighbors()] = (t2*Sx - 1j*t2*Sy)/2
syst.attach_lead(lead_left)
syst.attach_lead(lead_left.reversed())
return syst
def main():
# parameters
# create system
syst = create_system(length=10).finalized()
# plot the system and dispersion
kwant.plot(syst)
kwant.plotter.bands(syst.leads[0], show=False)
plt.plot([-np.pi, np.pi], [chemical_potential, chemical_potential],
'k--')
plt.show()
lead = syst.leads[0]
bands = kwant.physics.Bands(lead)
momenta = np.linspace(-2*np.pi, 2*np.pi, 401)
energies = [bands(k) for k in momenta]
plt.plot(momenta, energies,linestyle='--')
plt.xlim(-2*np.pi, 2*np.pi)
#pyplot.ylim(-5, 5)
plt.xlabel("$k$")
plt.ylabel("Energy")
#pyplot.axhline(y=0.0, color='k', linestyle='-')
plt.tight_layout()
plt.grid()
plt.show()
plt.close()
if __name__ == '__main__':
main()
________________________________________________
Thanks in advance,
*_________________________________*
*Subhadeep Chakraborty*
*_________________________________*
import kwant
import numpy as np
import math
##
import matplotlib
#matplotlib.use('Agg')
##
# For plotting
from matplotlib import pyplot as plt
# For matrix support
import tinyarray
I2 = tinyarray.array([[1,0], [0,1]])
Sx = tinyarray.array([[0,1], [1,0]])
Sy = tinyarray.array([[0,-1j], [1j,0]])
Sz = tinyarray.array([[1,0], [0,-1]])
Sp = tinyarray.array([[0,2], [0,0]])
Sm = tinyarray.array([[0,0], [2,0]])
def create_system(length=10):
t1 = 0.5 ; t2 = 1.0 ;
def Onsite(site):
(x, ) = site.pos
potential = x
return x
# system building
lat = kwant.lattice.square(a=1, norbs=2)
syst = kwant.Builder()
# central scattering region
syst[(lat(x, 0) for x in range(length))] = t1*Sx
syst[lat.neighbors()] = (t2*Sx - 1j*t2*Sy)/2
# add leads
sym = kwant.TranslationalSymmetry((-1, 0))
lead_left = kwant.Builder(sym)
lead_left[lat(0, 0)] = t1*Sx + Onsite*I2
lead_left[lat.neighbors()] = (t2*Sx - 1j*t2*Sy)/2
syst.attach_lead(lead_left)
syst.attach_lead(lead_left.reversed())
return syst
def main():
# parameters
# create system
syst = create_system(length=10).finalized()
# plot the system and dispersion
kwant.plot(syst)
kwant.plotter.bands(syst.leads[0], show=False)
plt.plot([-np.pi, np.pi], [chemical_potential, chemical_potential], 'k--')
plt.show()
lead = syst.leads[0]
bands = kwant.physics.Bands(lead)
momenta = np.linspace(-2*np.pi, 2*np.pi, 401)
energies = [bands(k) for k in momenta]
plt.plot(momenta, energies,linestyle='--')
plt.xlim(-2*np.pi, 2*np.pi)
#pyplot.ylim(-5, 5)
plt.xlabel("$k$")
plt.ylabel("Energy")
#pyplot.axhline(y=0.0, color='k', linestyle='-')
plt.tight_layout()
plt.grid()
plt.show()
plt.close()
if __name__ == '__main__':
main()
