Dear Kwant users and developers,

Is there a way to calculate the integral(< u_nk | d_k(u_nk)>dk)  across the 1D BZ of a system periodic in one direction. Here u_nk is the periodic part of the Bloch wave function corresponding to band n. I am trying to compute this for a simple system of graphene nanoribbon.

I am trying compute the gauge independent value of the above integral using a "1D Wilsoon loop" where the integral is approximately equal to the product of <u_nk|u_n(k+1) >  for all k across the BZ.  I defined the unit cell of the nanoribbon as a lead and tried to get the u_nk as the propagating modes using leads.modes() method (I have pasted the code below) but the resolution in k is too large - only 4 momenta across the BZ.

How can we get u_n(k) with a good resolution of k, say for 100 points in the BZ ? Is this something which can be easily done in Kwant ?

Code:

def make_1D_zigzag(N=7,t=1):
syst = kwant.Builder(kwant.TranslationalSymmetry(Zigzag.prim_vecs[0]))
syst[Zigzag.shape((lambda pos: pos[1] >0 and pos[1] < get_width(N)),(0,0))] = 2*t
syst[Zigzag.neighbors()] = -t
return syst