The lengths of scattering region and spin polarization.

1. This suggests to me that you haven't screened off your electrodes sufficiently. TranSiesta is based on *bulk* electrodes, and thus the electrostatics needs to be bulk-like at the electrode region of the scattering device. I.e. I(V) should not be length dependent if you simply add more electrode layers.

2. The total current is I = I(spin-up) + I(spin-down). In general I(spin-up) need not be equal to I(spin-down).

Many thanks for you quick answer, Nick Papior~

1. I will make more test calculaions.

2. When I open the spin polarizaions, the I(spinup)+ I(spindown) is not equal to the I (total) without spin polarization.

For example, same structure;

Under bias voltage: 1.5V
no spin polarization: I (total) = 0.8062E-05

Currents (ensure entire Fermi function window):
Left -> Right, V [V] / I [A]: 1.50000 V / 0.806203E-05 A
Left -> Right, V [V] / P [W]: 1.50000 V / -.602797E-05 W

open spin polarization: I (spin up)= 0.68E-05A I (spin down)=0.73E-05

Currents (ensure entire Fermi function window):
Left -> Right, V [V] / I [A]: 1.50000 V / 0.680710E-05 A
Left -> Right, V [V] / P [W]: 1.50000 V / -.519714E-05 W

Currents (ensure entire Fermi function window):
Left -> Right, V [V] / I [A]: 1.50000 V / 0.732193E-05 A
Left -> Right, V [V] / P [W]: 1.50000 V / -.547095E-05 W

I wonder that is there anything wrong with my calculations?

1. Good.

2. Of course, it is a different Hamiltonian, the electronic structure for the non-polarized is not the average up/down. Secondly, TBtrans writes out the current for non-polarized as though it was one channel, i.e. you need to multiply by two for non-polarized calculations.

Thanks Nick Papior, that solved my question.

Dear Nick,

Does the output current I of the non-polarized calculation of the magnetic systems meaningful?( In my test, the output current cof a magnetic system with non-polarized calulation is not equal spinup plus spindown or ethier of them) Or a spin-ploarized calculation of magnetic system is a must and the Total current = I (spin up) + I (spin down) ?

Many thanks for your previous detailed answers~~

Dear Nick,

Does the output current I of the non-polarized calculation of the magnetic systems meaningful?( In my test, the output current cof a magnetic system with non-polarized calulation is not equal spinup plus spindown or ethier of them) Or a spin-ploarized calculation of magnetic system is a must and the Total current = I (spin up) + I (spin down) ?

Many thanks for your previous detailed answers~~

Please see my answer 2 in my last comment.

They are not equal.

Dear Nick,

Thank you for your detaied answer~

Here, I still have this doubt: If a spin-ploarized calculation of magnetic system is a must? Or, the right way to get the total currents of a magnetic system under bias voltages?

Thanks you again~!

Thanks Nick Papior, that solved my question.