Hi again,

Thanks, I will try to write it more clearly. So the script I use to make the system is:

L = 100
W = 40
a = 1
t = 1

def make_system(W,L,a,t):

# Make the lattices
# We define two lattices (up and down) with two sublattices A and B
lat_up = kwant.lattice.general([(a,a),(a,-a)],[(0,0),(a,0)], name='up')
A_up, B_up = lat_up.sublattices
lat_down = kwant.lattice.general([(a,a),(a,-a)],[(0,0),(a,0)], name='down')
A_down, B_down = lat_down.sublattices

# Define the shape of the scattering region. Must return true where there are sites.
def shape_sr(pos):
x, y = pos
return ((0 < x < L) and (0 < y < W))


sys = kwant.Builder()

sys[lat_up.shape(shape_sr, (1,1))] = 2
sys[lat_down.shape(shape_sr, (1,1))] = 2

sys[A_up(1,1), A_down(2,1)] = 2

return sys

The error message I get is:
KeyError: Site(kwant.lattice.Monoatomic([[1,1], [1,-1]], [0,0]. 'up0'), array([1, 1]))

I can not see why the spot should not be created, because it is within the bounds of shapre_sr.

Thanks,

Best,
Camilla

-----Original Message-----
From: Anton Akhmerov [mailto:anton.akhmerov@gmail.com]
Sent: 31. oktober 2016 12:04
To: Camilla Espedal <camilla.espedal@ntnu.no>
Cc: kwant-discuss@kwant-project.org
Subject: Re: [Kwant] Hopping between different lattices and families

Hi Camilla,

Please double-check the error message that you see.

Your assumption why the code doesn't work is not right: it's possible to add a hopping from any site to any site, regardless of distance or lattices involved. My best guess is that the sites aren't present in the system yet.

As a general advice, when describing a problem try to provide complete information required to reproduce this problem. A script and the error message would be usually useful.

Best,
Anton

On Mon, Oct 31, 2016 at 6:58 AM, Camilla Espedal <camilla.espedal@ntnu.no> wrote:
> Hi again,
>
> I tried to add
>
> sys[A_up(2,2), B_down(2,2)] = 2
>
> This does not work, and I think it is because A_up and B_down are not
> only on different sublattices, but on different lattices as well. In
> the tutorial on superconductors
> (https://kwant-project.org/doc/1.0/tutorial/tutorial5#lattice-descript
> ion-using-different-lattices) they define the hopping as
>
> sys[((lat_e(x, y), lat_h(x, y)) for x in range(Deltapos, L)
> for y in range(W))] = Delta
>
> between the lattices but on the same spatial point. But I want to hop between two different lattices from one point in space to another, if that makes sense.
>
> Best,
> Camilla
>
> -----Original Message-----
> From: Anton Akhmerov [mailto:anton.akhmerov@gmail.com]
> Sent: 31. oktober 2016 11:48
> To: Camilla Espedal <camilla.espedal@ntnu.no>
> Cc: kwant-discuss@kwant-project.org
> Subject: Re: [Kwant] Hopping between different lattices and families
>
> Hi Camilla,
>
> It's exactly like you would expect: syst[A_up(i, j), B_down(i, j)] =
> value. See e.g. https://kwant-project.org/doc/1/tutorial/tutorial4
>
> Best,
> Anton
>
> On Mon, Oct 31, 2016 at 6:43 AM, Camilla Espedal <camilla.espedal@ntnu.no> wrote:
>> Hi,
>>
>>
>>
>> To explain what I mean. I have a system where I have separated
>> spin-up and spin-down into two lattices (like electron and hole in
>> the example at the kwant site) so that it is would be easier to
>> extract spin-resolved information (G_up/up, Gup/down etc.). In
>> addition, these two lattices consists of two sublattices (A and B).
>> The code is like this
>>
>>
>>
>> lat_up =
>> kwant.lattice.general([(1,0),(s,c)],[(0,0),(0,1/sqrt(3))],
>> name='up')
>>
>> A_up, B_up = lat_up.sublattices
>>
>> lat_down =
>> kwant.lattice.general([(1,0),(s,c)],[(0,0),(0,1/sqrt(3))],
>> name='down')
>>
>> A_down, B_down = lat_down.sublattices
>>
>>
>>
>> What I want to do now, is to add a hopping term between say A_up
>> (i,j) and B_down (i.j). So a hopping term between the two different
>> lattices and sublattices. How can I implement this? Or is there a
>> better way to achieve what I want?
>>
>>
>>
>> Best
>>
>> Camilla Espedal