Spin polarized temperature dependent current for two probe device

[physics]

Hi everyone,

While doing temperature dependent spin polarized current calculation, what is the direction of current if left electrode is at high temperature and right electrode is at low temperature. In some cases the up spin is in negative in sign and lower in magnitude than down spin, what could be possible explanation? Also, is it possible that total current (up spin+down spin) flow from cold electrode to hot electrode?

Thank you

[Anders Blom]

Yes I suppose it can, it depends intricately on how the bands align and the population of each side according to temperature.

[physics]

Hello,

The current should flow from high temperature to low temperature. How it is flowing in opposite direction? From where I can read more about it?

Thank you

[Anders Blom]

For some reason I believed that your structure was heterogeneous, i.e.. different materials on the left and right. If not, then it should make the analysis a bit simpler of course.

It's still hard to make a statement about your results as so few details are provided. "Some cases" can mean some bias points, or some other modifications done to the system...

Specifically, the current is computed from the formula found here:
https://docs.quantumatk.com/manual/Types/TransmissionSpectrum/TransmissionSpectrum.html#current
While the transmission is always positive, the actual sign of the current comes from the difference in populations via the Fermi functions, and can be complex.

Also note that if the current is very small, numerical errors can play a role, but again without details, it's very difficult to speculate.

[physics]

Hello,

Thank you for the reply. Yes, the structure is a heterostructure having same type of electrode on both the sides. For some temperature difference  between left and right electrode,(let's say for TL= 300 K, 400 K) the current is flowing from hot to cold (positive current) while for some (let's say for TL= 500 K) it changes sign and flow from cold to hot (negative current). Could you please let me know how I explain this phenomena or suggest me some references. It is confusing me a lot.

Thank you

[Anders Blom]

Not sure if this helps maybe?
https://byjus.com/physics/seebeck-effect/