Can anybody help me with the concept "contributions" in tranmissionpathway?

[lknife]

Dear experts,

I am not sure of the meaning of this sentence " The transmission pathways contributions from the left or right electrode" when I tried to calculate the transmissionpathway of a two-probe device under a certain bias.

What's the difference: contribution from left or right electrode?

Please see the attached picture. It's the transmission pathway of a in-plane hetero-junction. I don't know what's the thickness of the lines stands for.

Does  the thickness of the transmission lines stand for the magnitude of the current flow? But according to my knowledge, the current flow from one electrode to another electrode should be the same along the transport direction. I don't know why there is no transmission lines near the right electrode.

Any other explanations to the question? I forgot if I used the default setting of the transmissionpathway (contribution from left). Do I need to recalculate the transmissionpathway with "contribution from right electrode"?

I appreciate your kind help!

[Jess Wellendorff]

I think the ATK Manual explains it rather well:  https://docs.quantumwise.com/manuals/Types/TransmissionPathways/TransmissionPathways.html
Default contributions is Left, meaning you study the transmission pathway for electron originating in the left electrode and transmitted to the right electrode. I would say no, you do not need to redo the analysis with contributions=Right.

"Arrows point in the direction of the pathways. The magnitude of the pathway is illustrated by the volume of the arrow and the color shows the direction"

"The local bond contributions, T_ij, can be both positive and negative. A negative value correspond to that the electron is back scattered along the bond. A positive value of T_ij  is visualized as an arrow from i to j, while a negative value is visualized as an arrow from j to i, i.e. the direction of the arrows shows the flow of the electrons.

[lknife]

Thank you very much for your valuable reply.

There are some other questions:

(1)  Since the potential of the left electrode is higher than that of the right electrode (because of the bias), the actual transport direction of the electrons shoud be from the right electrode to the left electrode. That is, the electrons originate from the right electrode and then transport to the left elelctrode.  In other words, I should calculate the transmission pathways with contributions=right.  Is it right?
If the actual transport direction for the electrons is from the right electrode to the left electrode and I calculated the transmission pathways with contributions=left, is there any problems doing like that?

(2) How to check the T_ij? There is no such parameter in the settings of the transmissionpathway in the Viewer. Do I need to check it from the text representabion of the transmissionpathway? 

(3) How to set the energy value when I set the parameters for the  tranmissionpathway calculation? Do I need to set the energy value according to the transmission spectrum? That is, to set the energy to the value when it shows relatively high transmission spectrum?
 
Thank you very much again for your kind help!

[Jess Wellendorff]

(1) Yes, under forward bias (where the electrons move from right to left) it probably makes good sense for you to do the TransmissionPathways analysis using Right contributions.
(2) As writtin in the ATK Manual, https://docs.quantumwise.com/manuals/Types/TransmissionPathways/TransmissionPathways.html, the method "evaluate()" should give you the data you are looking for. This should also be what the Text Representation gives you. You could also try to nlprint the TransmissionPathways object.
(3) Default electron energy for evaluation the transmission pathways is at the average Fermi level. You may choose a different energy, but be aware that the current-carrying states will in general be the ones in the energy window between the electrode Fermi levels.

[lknife]

Thank you very much again for your kind help!