modes and current density
Hello everyone, I want to compute and plot the current density in a graphene sample. I logically use kwant.operator.Current(syst) and then kwant.plotter.current(syst, current) to plot the current density in the sample. However, the main example in the kwant documentation only uses the wavefunction associated to the first mode to compute J: ________________________________ wf = kwant.wave_function(syst, energy=0.3) J0 = kwant.operator.Current(syst) wf_left = wf(0)[0] current = J0(wf_left) ________________________________ In my case, I have a system with more than one mode. I have found some lines that consider all the modes (at the end of this page : https://kwantproject.org/doc/dev/tutorial/operators ) 2.7. Computing local quantities: densities and currents ...<https://kwantproject.org/doc/dev/tutorial/operators> kwantproject.org 2.7. Computing local quantities: densities and currents¶ In the previous tutorials we have mainly concentrated on calculating global properties such as conductance ... ________________________________ wf_left = wf(0) J_m_left = sum(J_m_bound(p) for p in wf_left) J_z_left = sum(J_z_bound(p) for p in wf_left) ________________________________ But this is equivalent to calculate the expression [cid:96ff5a324b824677ab3d04d9e9e1233e] which is simply the sum over the current coming from each mode. However, I would have rather use the following expression to find a more general expression of the current density [cid:a1236ff5dbcc445a98b4712fc485334f] What is therefore the good way to find J? I have not found more informations in the Kwant documentation. Best regards, Nicolas
Hi,
 In my case, I have a system with more than one mode. I have found some lines that consider all the modes (at the end of this page : https://kwantproject.org/doc/dev/tutorial/operators) 2.7. Computing local quantities: densities and currents ... <https://kwantproject.org/doc/dev/tutorial/operators> kwantproject.org 2.7. Computing local quantities: densities and currents¶ In the previous tutorials we have mainly concentrated on calculating global properties such as conductance ...
 wf_left=wf(0) J_m_left=sum(J_m_bound(p)forpinwf_left) J_z_left=sum(J_z_bound(p)forpinwf_left)  But this is equivalent to calculate the expression
which is simply the sum over the current coming from each mode. However, I would have rather use the following expression to find a more general expression of the current density
What is therefore the good way to find J? I have not found more informations in the Kwant documentation.
Best regards,
Nicolas
If you want to calculate the total current at a given energy you really should sum the contributions from each mode independently! You say that the "more general" expression for the current density is: but I'm not sure what you mean by that. In the above expression you are making some weird kind of mix of different modes. This is certainly not the expectation value of the current operator; are you maybe trying to calculate some kind of noise properties? Regards, Joe
participants (2)

Joseph Weston

Nicolas Moreau