Hi Kristjan, 1) First of all, I suspect that infinitely wide leads (somehow by using additional translational symmetry for leads and the wraparound module), which would result in plane waves without the transversal energy quantization are not possible. Is this correct? Ideally I would like the result to be independent of the y position of the potential barrier hole (i.e. independent of the hole_y variable). In order to get a correct result for conductivity you should integrate over the lattice momentum in y-direction. If all is done correctly, the result will indeed not depend on the position of the hole. 2) If I calculate transmission for a given energy value, is the k vector of the incoming electron wave (and thus the "effective" orientation of the lead) given by k=(kx, ky), where kx is given such that the specified energy is obtained (taking into account that the transversal quantization energy is subtracted for a given mode)? The momentum reflection from the hole is conserved modulo the periodicity of the system in the y-direction, so the transmission is computed for all the incoming waves with k_y mod 2 pi / L = k_{y, superlattice}, where L is the periodicity of the unit cell in the y-direction, and k_{y, superlattice} is the momentum parameter provided to wraparound. 3) Is the reflection and transmission calculated only in the direction of the leads and the reflection and transmission in arbitrary directions is not taken into account (see figure for details)? The reflection matrices are computed for a specified value of k_{y, superlattice}, and in order to get full conductance you should integrate over all k_{y, superlattice}. Hope this helps, Anton On Mon, Feb 20, 2017 at 10:13 PM, Kristjan Eimre wrote:

Hello Kwant community,

I am trying to model transport across an infinite potential barrier plane with the wraparound module. My current code is here: http://pastebin.com/ux1PwvXS

I have been trying to follow the guidance provided in this comment: https://www.mail-archive.com/kwant-discuss@kwant-project.org/msg00873.html

The system setup is simple, it has a rectangular finite width (in x direction) barrier with potential V0 with a hole in the middle with potential V_hole. In y direction, the barrier is periodic (so the holes are infinitely repeating). I hope that this is correctly implemented in the code.

The wraparound module is used on this barrier, making the system finite in y direction and creating a new parameter called ky.

I have multiple questions about the parameter ky, leads and the physics. See the attached figure system_schematic.pdf for visual illustration.

1) First of all, I suspect that infinitely wide leads (somehow by using additional translational symmetry for leads and the wraparound module), which would result in plane waves without the transversal energy quantization are not possible. Is this correct? Ideally I would like the result to be independent of the y position of the potential barrier hole (i.e. independent of the hole_y variable).

2) If I calculate transmission for a given energy value, is the k vector of the incoming electron wave (and thus the "effective" orientation of the lead) given by k=(kx, ky), where kx is given such that the specified energy is obtained (taking into account that the transversal quantization energy is subtracted for a given mode)?

3) Is the reflection and transmission calculated only in the direction of the leads and the reflection and transmission in arbitrary directions is not taken into account (see figure for details)?

I apologize if the questions are basic or unclear, hopefully you can give some insight into the problem or tell me if I have fundamentally misunderstood something.

Best regards, Kristjan