Dear Sudin,
Just to add to Christoph's reply, there's an example of Hall and
longitudinal conductance calculated over here:
http://nbviewer.ipython.org/github/topocm/topocm_content/blob/master/w3_pump...
(to see the code, click the button at the top of the notebook). You
may find this useful.
Best,
Anton
On Wed, Mar 18, 2015 at 10:36 AM, Christoph Groth
Sudin Ganguly wrote:
nonlocal_resistance = np.linalg.solve(cm, [1, 0, -1])[1]
Why did you put the currents I_0=1, I_1=0 and I_2=-1?
The code line you cite is taken from the valve.py example script From the Kwant paper. Did you have a look at the full example that can be downloaded at http://downloads.kwant-project.org/examples/kwant-examples-njp.zip?
Non-local conductance measurements in the Landauer-Büttiker formalism are explained in Sec. 2.4 of the book by S. Datta “Electronic transport in mesoscopic systems”.
In short it works like this: In the cross geometry, we want to measure the Hall resistance, that is the transverse voltage divided by the longitudinal current when there is no transverse current. Thus, we set the longitudinal current to 1 and the transverse current to 0. The Hall resistance is then given by V[1] - V[3] = V[1].
Christoph