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 <[email protected]> wrote: > 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: [email protected] > ===================================== > ᐧ >
