Hi Daehan,
This happens because the tight binding models have a finite band width.
Compare your results with a band structure of the model you are considering.
Best,
Anton
On Thu, 12 Mar 2020 at 09:00, dae han Park
Hello.
My name is Daehan Park. I am a new user for Kwant.
To accustom me to using Kwant, I start to attack simple quantum mechanics problems in kwant program.
In below code, I try to solve a simple square barrier problem. ================================================================== import kwant import math from matplotlib import pyplot syst = kwant.Builder()
wire = kwant.lattice.chain(1) t = 1.0 # hopping parameter W = 100 # the number of atoms in the direction of width
for i in range(W): # on-site Hamiltonian syst[(wire(i))]=2*t
for i in range(10): # on-site Hamiltonian syst[(wire(i+10))]=2*t + 0.5
syst[wire.neighbors()] = -t # hopping
# attaching leads sys_left_lead = kwant.TranslationalSymmetry([-1]) left_lead = kwant.Builder(sys_left_lead) left_lead[wire(0)] = 2*t left_lead[wire.neighbors()] = -t syst.attach_lead(left_lead) syst.attach_lead(left_lead.reversed())
kwant.plot(syst) sys = syst.finalized()
def plot_conductance(sys, energies): # Compute conductance data = [] for energy in energies: smatrix = kwant.smatrix(sys, energy) data.append(smatrix.transmission(1, 0))
pyplot.figure() pyplot.plot(energies, data) pyplot.xlabel("energy [t]") pyplot.ylabel("conductance [e^2/h]") pyplot.show()
plot_conductance(sys, energies=[0.01* i + 1e-6 for i in range(500)]) ========================================================================
The outcome above the code is as following;
[image: image.png]
My question is why conductance becomes zero when the incident energy is over 4.
Thank you for reading my e-mail
Sincerely, Daehan Park.
===================================== Department of Physics, Soongsil University, 369, Sangdo-ro, Dongjak-gu, Seoul 156-743, Republic of Korea (South Korea) mail: m31phy@gmail.com ===================================== ᐧ
