Hi Joe, The main reason for wanting to have the contact wrap around a corner, and not just add cells to the scattering region, is that it will act as a dephasing boundary when we perform Landauer-Buttiker equation calculations. I don't want to plug my own paper, but we recently wrote up a manuscript where this can be done with a virtual contact, except it was just a straight contact on the side of the device (it is on arXiv). Now I am hoping to extend that to where the contact wraps around. In this way you could engineer where dephasing happens in a device- something we are also trying to achieve in the lab. You can sort of do this with Kwant by making two virtual contacts as I showed and then fixing them to the same voltage in the Landauer-Buttiker calculation, however the waves injected from the two contacts are out of phase with one another and will not interfere. I don't think that is a huge issue, but it is not ideal. Something which I think is related to this, would be to create some sort of isotropic source inside of a sheet by wrapping a contact around the interior of a hole. Currently the best way I have seen to inject electrons isotropically (or close) in the middle of a scattering region is as was shown in the Hanle valve example. Unfortunately, I have not found a good way to make these leads couple to the scattering region well. Maybe there is some other way to achieve this? Thanks! Sam ________________________________________ From: Joseph Weston <joseph.weston08@gmail.com> Sent: Thursday, April 13, 2017 9:58 AM To: LaGasse, Samuel Cc: kwant-discuss@kwant-project.org Subject: Re: [Kwant] Wrapping leads around a channel Hi Sam, Thanks for the clarification.
I'm trying to study a system where a contact has been patterned around the outer edge of a channel. Initially I have tried attaching one lead oriented along the z-direction (similar to the Hanle valve example in the Kwant paper), which allows me to make one lead which boarders two sides of the device (and vertical leads in the middle).
My hope is to somehow construct one contact (with 1 translational symmetry) that has a width of the perimeter of the red line in my diagram. I would like to then attach the contact in such a way that it bends around the corner. It sounds like this would not be possible though.
What is it that you are hoping to acheive with the contact that "bends round the corner? Naively I would say that you could construct the system that I have attached as an image. Essentially you would just add the part of the lead that "bends round the system" as an explicit part of the scattering region. What were you hoping to achieve by attaching two leads in the first place? Joe