Dear kwant community:
I am investigating the `kwant.greens_function`。 I would like to get the lead
self-energies and add to the original system Hamiltonian and then inverse it,
thus obtaining the retarded green's function. I tested, but the resulted
green's function is not identical to the one kwant calculated. I want to know
the reason. Is it because what I describe in the title?
Below is a minimal code example:
```
lat = kwant.lattice.square()
def make_system(r=20, t=-1):
def circle(pos):
x, y = pos
return x**2 + y**2 < r**2
syst = kwant.Builder()
syst[lat.shape(circle, (0, 0))] = 0
syst[lat.neighbors()] = t
syst.eradicate_dangling()
def lead_shape(pos):
return -12 < pos[0] < 12
lead = kwant.Builder( kwant.TranslationalSymmetry((0, 1)))
lead[lat.shape(lead_shape, (0, 0))] = 0
lead[lat.neighbors()] = -t
syst.attach_lead(lead)
return syst
syst = make_system()
fsyst = syst.finalized()
kwant.plot(fsyst)
greens_function=kwant.greens_function(fsyst)
Hc = fsyst.hamiltonian_submatrix(sparse=False)
index = fsyst.lead_interfaces[0]
Hc[np.ix_(index, index)] += greens_function.lead_info[0]
Gr = np.linalg.inv(-Hc)
Gr[np.ix_(index, index)]-greens_function.submatrix(0, 0) # should be a zero
matrix
```
Bests,
Wilson
