Hi Anant, You wrote:

Is there any way in KWANT that I can plot a 3-d graph of dispersion relation? In the tutorial it is given that the infinite system is quasi 1-d system.

Indeed, in Kwant 1.x low-level systems (e.g. finalized builders) can only be either finite or quasi-1-d. This is because we added the concept of symmetries to Kwant only after the basic low-level design was already fixed. We plan to remove this restriction in the next major version of Kwant. For now, you can use a variant of the trick mentioned in http://article.gmane.org/gmane.comp.science.kwant.user/39. As an example, I attach a script that calculates and plots the band structure of graphene. The 6 k-points are clearly visible. With Kwant 2, an equivalent script will be less “hacky”.

that means is it only giving values for Kx momentum.I guess not. I guess it is the values of energies for momentum K = -sqrt(Kx*Kx + Ky*Ky) and K = +sqrt(Kx*Kx + Ky*Ky).

I’m not sure what you mean by this. Best Christoph