Right. That's what I thought. However just wanna point out the original example code kernel_polynomial_method.py was buggy and doesn't give the delta function for this identity matrix. I managed to get it almost right by changing some lines. But right now it's shifted instead of being a peak at 1.

Best wishes, Edmond

On Tue, Jun 9, 2020 at 2:16 PM Anton Akhmerov <anton.akhmerov+kd@gmail.com> wrote:

Hi Edmond,

You are plotting the spectral density of the identity operator, which
is the same as the density of states. If you were plotting the density
of states of an identity operator, you'd see a delta-function peak
indeed. Please review the definitions in the tutorial:
https://kwant-project.org/doc/1/tutorial/kpm#calculating-the-density-of-states

Best,
Anton

On Tue, 9 Jun 2020 at 00:47, <edmondztt@gmail.com> wrote:
>
> BTW the result I got from this code looks exactly the same as the graphene case. For an identity matrix it should be a flat band and the DOS should just show a peak, right?