Hello Kwant Community, I created a 3D nanowire grown along x direction with leads attached in the x direction and want to plot the current density profile through a cut at a x = const plane. I think this Problem was never really solved in the public community communication channels, and personally I think this is quiet useful, because people might want to show surface currents of TI's etc.
I created a minimal example displaying two methods to calculate and display the current density through a plane x = const: see my jupyter notebook on GitHub: https://github.com/Quaki96/KwantQuestion_2D-current-density-profile-through-3D-nanowire-cut/blob/4dde2854731c3f787c294779b9d13907002acba5/current_density_minimal_example.ipynb There at "# current density through x=const plane METHOD 1": I build a 2D slice of the 3D nanowire and use kwant.operator.Current(fsyst, where=cut) and specifying for which hoppings in should calculate the current density: def cut(site0,site1): return site0.pos[0]==x_cut and site1.pos[0]==x_cut+1 # calculating current just for this x hopping This yields a current density profil with only non negativ current densities even if I have no magnetic field, hence this somehow breaks time reversal symmetry. If I instead define def cut2(site0,site1): return site0.pos[0]==x_cut+1 and site1.pos[0]==x_cut # calculating current just for this x hopping I get the same picture except that the sign changed completely. "# current density through plane x = const METHOD 2 Here I use kwant.operator.Current(fsyst), and calculate the current density over all hoppings of the system. Then I use kwant.plotter.interpolate_current(fsyst, current_density) to interpolate the current density vectorfield which returns it as field, box. In a simple inefficient for loop I then create an array of y_vals and z_vals and their corresponding current density z (2) component values = values.append(field[x_cut,ny,nz,2]) at x = x_cut. This yields a current density profile which seems to respect time reversal symmetry (vanishes when B = 0) is non zero when B != 0 but because no bias is applied integration over the plain yields zero total current. I think this might be a correct implementation. But I am really not sure because I don't know what I might did wrong in the first implementation. Happy Kwanting Felix
