Hello,
I'm a graduate student in Jeff Neaton's group at Berkeley and am currently using Z2pack to study a few of my systems. It's been going well so far, but I had a few questions if you would be able to provide some guidance.
One of my systems is a Dirac nodal line and I wanted to compute the Berry phase using a ring around the nodal line to show it's nontrivial. I can see how to do it for the case of a single Dirac point with the Sphere in the shape module, but is that the only shape currently implemented? Is there a "ring" to use as the shape for line.run()?
The nodal line is in the kz=0 plane, so one thing I've tried so far is finding the point on the nodal line with a minimal kx value and then calculating one string around the sphere still using the surface module. However, I'm not sure how to specify I want the line to be at constant x and just traverse around the sphere in the y-z directions.
Another idea I was trying was to add a "class" to the shapes.py module for a ring, just based on the sphere one that's already there, the only difference being that I don't update the x value. (I realize this is very system specific and not a general solution). It's not clear to me how line.py actually iterates around this ring to calculate the wannier charge centres (and thereby get the Chern number).
Do either of these seem plausible? I could also send my inputs and/or errors if you want. Although if there's already something implemented I've missed please let me know...
Lastly, one quick question, would you mind clarifying if the coordinates for the centre of a sphere should be given in cartesian or direct coordinates?
Thank you in advance for any feedback!
Best, Stephanie