Tr (k, e)/shift in Fermi level

[Dipankar Saha]

Hello,
One more thing ...that I find a bit confusing is__

We may obtain the conductance (or, say thermal conductance due to the contributions of the charge carriers) with help the "plugin"..../ Whatever the value that we  get...are they calculated under the linear aprrox. ??

Again,  using the same transmission co-eff.  we do calculate SCF-current also..., but I don't think there is any approximation of linear coherent transport...!!! Isn't it?!!

Best_
Dipankar

[Jess Wellendorff]

Yes, as explained in http://quantumwise.com/documents/tutorials/latest/Phonon/index.html/chap.thermoelectric.html, the VNL plugin "Thermoelectric Coefficients" calculates various electronic and vibrational transport coefficients in the linear response regime.

I presume that by "SCF-current" you mean the electrode-to-electrode current derived from a TransmissionSpectrum after SCF is converged. The last sections of http://www.quantumwise.com/documents/manuals/latest/ReferenceManual/index.html/chap.negf.html#sect1.negf.current indicate that the energy-dependent device transmission coefficient may be considered a sum of transmission amplitudes at each particular energy.

[Dipankar Saha]

Thank you Jess...for the reply...!! 

the electrode-to-electrode current derived from a TransmissionSpectrum after SCF is converged...

Not exactly that... I meant the calculations of Tr(e) for individual bias voltages..... / However...what that I was asking ....is somewhat related to the Fermi distribution func. of the electrodes. Meaning, if there is not any approximation of linear coherent transport (considering the case of I-V calculation).........then the f_L,R(mu, T_L,R) should not be approximated or, simplified...!!! Is it not??
Regards_
Dipankar

[Dipankar Saha]

Besides, we know that the Tr_e is insensitive to the temp . change....  But G(E) shows a significant variation with temp. If it's a linear electronic conductance...in that case...the only way you can include temp. effect is through the L_0 ... (again, del_T is also zero)....!! Correct??
However, for the other calculations (under the same linear response approx.)...e.g, "S" or, "K_e"...a del_T value should be reqd. ......How do you incorporate the "del_T"  ....given a particular temp. T, say, 100 K, 200 K  or, anything ??

[kstokbro]

The temperature enters the formalism through the fermi function, so it is an electron temperature.
Forinstance, at T=0 the conductance is given by the transmission coefficient at the fermi level, while for a finite temperature the transmission is averaged around the fermi level using the fermi function.

[Dipankar Saha]

Dear Dr. Kurt Stokbro,

Thank you very much for the reply.... 
________
So, in Near-equilibrium..if we take Taylor’s series expansion....of the f(E, mu_l) -f (E, mu_R) ...then I have two terms... In one of the terms ,  (-df0/dE) needs to be multiplied by del_V  .......and in case of the other one.... (-df0/dE) is multiplied by del_T   
How should we incorporate this  del_V....? Directly into the Landauer formalism?? Or else,  right from the NEGF calculation of the Transmission function...??
Regards_
Dipankar