Dear community,
I would like to calculate the valley polarized conductance for a graphene nanoribbon with 2 leads (let’s say in the x-direction). My current approach is this:
1) Get the S-matrix for a certain energy
2) Find the indices of the modes with positive velocities
3) Separate these modes by positive and negative momenta
4) Get the sub matrix from the S-matrix
5) Sum the transmission coefficients for positive and negative momenta
The code below illustrates these 5 steps:
import progressbar
def valleyPolarizability(syst, energies, lead_start=0, lead_end=1):
KPs = []
Ks = []
bar = progressbar.ProgressBar()
for energy in bar(energies):
smatrix = kwant.smatrix(syst, energy, params={'phi': phi})
positives = np.where(smatrix.lead_info[lead_start].velocities >= 0)[0]
momentas = smatrix.lead_info[lead_start].momenta[positives]
K_prime_indices = np.where(momentas < 0)[0]
K_indices = np.where(momentas >= 0)[0]
submatrix = smatrix.submatrix(lead_end, lead_start)
K_prime_T = np.absolute(np.sum(submatrix[:, K_prime_indices]))**2
K_T = np.absolute(np.sum(submatrix[:, K_indices]))**2
KPs.append(K_prime_T)
Ks.append(K_T)
return KPs, Ks
Could someone please let me know if this is the correct approach? Will the K_prime_indices and K_indices have the correct indexing in the sub matrix?
Thanks,
Kevin Ryczko
