Transmission eigenvalue and eigenstates

[iconxicon]

I have done a calculation on a  2 dimensional system with ATK to study it's spin-dependent transport properties. However after the transmission spectrum was generated, I can not calculate the transmission eigenvalue in one of the transmission "peak", let along eigenstates. (The "peak"s transmission is about 0.15. )

After I tried to calculate the eigenvalue in VNL, I tried to use script, and ended up with the following sentence
"Number of transmission modes = 0"

Since I have obtained a rather big transmission coefficient, I think no transmission channel in this system is rather strange.

BTW, I have also calculated the same system under bias and the current is bigger (*10) than some other published research, although the transmission is about 3 orders below.

Can any one help please?

[Daniele Stradi]

Dear Iconxicon,
Could you please attach a script of your calculation and your reference data? It is difficult to figure out what it is actually wrong with the information you provided.
Thanks

[iconxicon]

THX for the reply
<1.py >corresponds with the pic I posted previous, <2.py> is a different but similar system with <1.py> except for the centre region (more layer to make sure it's a insulator), I calculated 2.py and found contradiction with other published research using ATK (DOI: 10.1103/PhysRevApplied.2.044008).

As you can see in <fig 2_pic.png> current is  1.05nA under the bias of 0.4 V, which I think is amazingly high (up 0.1496nA;down 0.900nA) consider around 0eV both up and down component's transmission is very low (magnified spectrum in <fig2_pic_mag.png>). And this contradicts with the paper I mentioned above whose transmission is higher than me but current lower.

[Daniele Stradi]

Dear iconxicon,

The number of transmission modes is zero because you are probably evaluating the transmission at the Gamma point. Instead, the peak at E-Ef = -0.45 eV is associated with transmitting states away from the Gamma point. Try with the Trasmission Analyzer to evaluate the eigenvalues at k_A = 0.0, k_B = 0.5, and you should get some eigenvalue. To do this you can set the values of k_A and k_B directly in the Bottom-Right panel of the Transmission Analyzer.

I am preparing a script to plot the k-resolved transmission, to make it easier to analyze.

Regarding the relation between transmission and current: I don't this the correlation is that straightforward, because in the Landauer formalism the current is calculated from the convolution between the Transmission and the Fermi functions of the electrodes. Therefore, also the electronic structure of the electrodes play a role.

[Daniele Stradi]

Another small comment, I think that the increase in the current with bias is due to the fact that at a bias of 0.4 V the tail of the resonance at -0.45 eV starts to enter the bias window.

[Daniele Stradi]

Dear iconxicon,

please find attached a script that reads a DeviceConfiguration, calculate the k-resolved transmission for a specified number of k-points, and save the results to a file that can be analyzed using VNL.

[iconxicon]

Thank you, Daniele, learned a lot!