Distinguisch Scattering matrix Elements
Hi everyone! I am a beginner Kwant consumer and, for this reason, I am trying to "solve" very simple problems, i.e. problems for beginners. The first one is the following: I have a 1D problem where basically a spin1/2 particle crosses a region without a potential neither magnetic fields. I am able to write correctly the setup of the problem in Kwant. Fixed the incoming particle energy, I find a 4 by 4 scattering matrix (this is comforting), but I do not understand which is the protocol that Kwant uses to order the coefficients in the scattering matrix. For example, according to the usual description of the transmission matrix (from lefttoright), the element t_{00} corresponding to the probability to start, for example, in the state s=1/2 in the left lead and arrives in the state s=1/2 in the right lead, and similarly for the other elements. How can I manage these labeling in my code? Thank you!
Dear Lorenzo, What you have explained is not enough to be of help. Meanwhile, I think it useful to have a look at previous discussions regarding using the conservation law to easily compute the spin conductance Ref*. You see bello a small script that might be useful: syst = kwant.Builder() sym = kwant.TranslationalSymmetry(lat.vec((1, 0))) syst = kwant.Builder(sym, conservation_law=sigma_z) smatrix = kwant.smatrix(syst.finalized(), energy, args=(params,)) # the spin up conductance (up to up) Gup.append(smatrix.transmission((1, 0), (0, 0))) # the spin down conductance (down to down) Gdn.append(smatrix.transmission((1, 1), (0, 0))) # total conductance G.append(smatrix.transmission((1, 0), (0, 0))+smatrix.transmission((1, 1), (0, 0))) Ref* https://kwantdiscuss.kwantproject.narkive.com/ZRoAKlBg/kwantupdowncondu... https://www.mailarchive.com/kwantdiscuss@kwantproject.org/msg00483.html best; Adel Le mer. 6 mars 2024 à 16:53, Lorenzo BAGNASACCO <lorenzo.bagnasacco@sns.it> a écrit :
Hi everyone! I am a beginner Kwant consumer and, for this reason, I am trying to "solve" very simple problems, i.e. problems for beginners. The first one is the following:
I have a 1D problem where basically a spin1/2 particle crosses a region without a potential neither magnetic fields. I am able to write correctly the setup of the problem in Kwant. Fixed the incoming particle energy, I find a 4 by 4 scattering matrix (this is comforting), but I do not understand which is the protocol that Kwant uses to order the coefficients in the scattering matrix. For example, according to the usual description of the transmission matrix (from lefttoright), the element t_{00} corresponding to the probability to start, for example, in the state s=1/2 in the left lead and arrives in the state s=1/2 in the right lead, and similarly for the other elements. How can I manage these labeling in my code?
Thank you!
participants (2)

Adel Belayadi

Lorenzo BAGNASACCO