Hi Jan,
I'm looking for a workaround for a problem I currently face: when computing the two-terminal conductance for a system of length L, is there a way to get the conductance for the same system of length 1,2,..L-1 on the fly (while keeping everything else the same, i.e., same width, same disorder configuration etc.)?
Kwant does not support this. You would need to construct a new system for each of these cases, which would incur the relatively high cost of system construction and finalization for every value of L. A possible workaround would be to construct the scattering system of length L, and then to add a parameter to your onsite/hopping functions that you can tune, such that your "effective" scattering region is whatever length you like. This would be faster, as you would only have to construct and finalize your system once.
As far as I understand how the scattering matrix calculation works internally, it shouldn't take much longer to compute these intermediate values than just getting the final conductance.
I'm not sure what you mean. The default scattering solver does not use the recursive Green's function method or anything. We (more or less) solve a linear system in the basis of modes in the lead, and local degrees of freedom in the scattering region, so that the total solution vector contains scattering matrix components in the "lead" part, and the scattering wavefunction in the "scattering region" part. We set up this linear system and then pass it off to a sparse linear solver (MUMPS by default). Given this, it is not immediately obvious to me how we would compute these "intermediate" values. Happy Kwanting, Joe