Transmission spectrum of CNT

[serhan]

Hi all,

When I calculate the transmission spectrum of an ideal CNT for different bias voltages in ATK , I see that the transmission spectrum changes by the bias voltage a lot. Is it normal, if it is normal what is the reason of the change of transmission spectrum bu bias voltage? Any references would be appreciated.

Cheers,
Serhan

[Nordland]

When a finite bias calculation is performed, an external field is introduced into the scattering region, and hence the potential that the electron feels when
traveling through the scattering region is different. Therefore the density of the central region will try to compensate for this potential, and hence it might create states that can cause either reflection or scattering of the propagating modes of the electrode.

It is very common that the transmission spectrum is altered strongly by the external field coming from the bias, and this is the reason why we need to perform calculations with NEGF.

However if your aim is too study a perfect system like the ideal CNT, then there is not natural place for the the voltage drop to occur, and therefore result might be come slightly artificial as you introduce as asymmetric potential in a perfect symmetric system. Therefore if your system is
an ideal, perfect system, I recommend using the linear response current function, as it will give you exactly want you want. The IV-curve of a infinite, perfect  system. 

[hellboy]

I performed Transmission spectrum calculation at zero bias and at 2 volts on a (8, 0) nanotube.

In case of T(E) at 2 volts bias, I found an increase in transmission width at 0 eV (Fermi level).
Is it possible ? Please look at the attached pictures of T(E).

[Anders Blom]

No offense, but basically you are using a very expensive method to calculate the number zero
A semiconducting nanotube will have no transmission as long as the bias is smaller than the band gap.