Dear All, I'm trying to calculate the site-to-site current with kwant, for a specific system, the output of "kwant.plotter.sys_leads_hopping_pos" is like below: (array([[-1., -1.], [-1., -1.], [ 0., 0.], [ 0., 0.], [ 1., 0.], [ 1., 1.]]), array([[ 0., 0.], [-2., -2.], [ 1., 1.], [ 1., 0.], [ 1., 1.], [ 2., 2.]])) For the current calculation of the same system, I use the command below: ------------------------------------------------------------------ wf = kwant.wave_function(syst, energy=-1) psi = wf(0)[0] J_0 = kwant.operator.Current(syst) current = J_0(psi) ------------------------------------------------------------------ and the out put of "current" is like below: [ 0.33230769 -0.33230769 0.33230769 0.22153846 -0.33230769 0.11076923 -0.11076923 0.11076923 0.33230769 -0.22153846 -0.11076923 -0.33230769] I'm not clear about the exact correspondance between the element of current (12 element) and the element of hopping (2 array), could you plese give me some explanations about this? Also, I'm not sure that if I want to calculate the current at a certain energy (like "-1" above), do I have to calculate the current at all the wavefunction (like for all p of wf(0)[p]) or I have to calculate the current only at the wavefunction with "negivate velocity"? Thanks in advance for your help. Hang Zang