Hi,
Hi, thanks for the quick reply. Correct. I wanted to attach the lead at the center of the sample. The reason for inputting 13 < x < 15 is by an analogy with the first pair of leads (which were placed at the edges).
OK, I've never seen anyone want to do this, especially for QHE in graphene where usually you just want some 4 or 6 terminal setup with the leads placed at the edges of the sample. To do what you want you're going to have to attach the lead manually. the `attach_lead` method is for attaching leads that come from infinity and interrupt the system at the edge; this is not the case that you have. It's kind of annoying to attach the lead manually so what you can do is the following. Attach the lead at the edge of the sample using `attach_lead`, and then move the sites in the interface to where you want them to be. You will then need to delete the sites which (may) have been added to the system in order to attach the lead at the edge. There is a minimal example as an attachment that just attaches the lead in the middle of the system and moves the interface. I hope that helps. Happy kwanting, Joe