Dear Yuhao, The Green's function between two sites in your case is a 2x2 matrix. This is due to the spin degree of freedom. So, getting 18x18 in your case is the correct result. I hope this helps. Adel On Tuesday, March 20, 2018, yuhao kang <kymwswj@gmail.com> wrote:
Dear Kwant developer,
I’m trying to calculate the greens function as follows:
gf = kwant.greens_function(sys,0).submatrix(1,0)
It returns a 18*18 matrix. Does it mean the green function between 18 points in lead0 to 18 points in lead1?
However, when I plot this system, there is only 9 points at each lead. If the base used here are not the lattice point?
Can I get the coordinates of the 18 points in both leads? So I can know the green function between two designated positions.
Thank you.
Best,
Yuhao
Here is my code.
##
import numpy as np
import kwant
m, t=0.4, -0.133
dis=0
a=1
lat = kwant.lattice.general([[a, 0], [a/2, a*np.sqrt(3)/2]],
[[0, 0], [0, a/np.sqrt(3)]])
A,B=lat.sublattices
sys=kwant.Builder()
s0=np.identity(2)
sx=np.array([[0,1],[1,0]])
sz=np.array([[1,0],[0,-1]])
def disk(pos):
x,y=pos
return abs(y)<2 and np.sqrt(3)*x-1<y<np.sqrt(3)*x+5
def edge(pos):
x,y=pos
return abs(y)<2 and np.sqrt(3)*x-0.1<y<np.sqrt(3)*x+0.58
def edge1(pos):
x,y=pos
return abs(y)<2 and np.sqrt(3)*x-0.1<y<np.sqrt(3)*x+0.58
def hopp(site1,site2):
x1,y1=site1.pos
x2,y2=site2.pos
if (y1+0.1*a)*(y2+0.1*a)>0 and y1+0.1*a<0:
return -t*s0
else:
return np.zeros([2,2])
def hopp2(site1,site2):
x1,y1=site1.pos
x2,y2=site2.pos
if (y1+0.1*a)*(y2+0.1*a)>0 and y1+0.1*a<0:
return t*s0
else:
return np.zeros([2,2])
def onsite(site):
x,y=site.pos
if (x-25*a)**2+(y-9*a)**2<8:
return -m*sz+0*sx
elif y>-0.1*a:
return m*sz+0*sx
else:
return np.zeros([2,2])
sys[lat.shape(disk,(0,0))]=onsite
sys[lat.neighbors()]=-s0*2/3
sys[A.neighbors()]=hopp
sys[B.neighbors()]=hopp2
lead0=kwant.Builder(kwant.TranslationalSymmetry((-a,0)))
lead0[lat.shape(edge,(0,0))]=onsite
lead0[lat.neighbors()]=-s0*2/3
lead0[A.neighbors()]=hopp
lead0[B.neighbors()]=hopp2
sys.attach_lead(lead0)
sys.attach_lead(lead0.reversed())
kwant.plot(sys, fig_size=(30, 12))
sys=sys.finalized()
gf=kwant.greens_function(sys,0).submatrix(1,0)
##
-- Abbout Adel