Author Topic: Green's function method T(E)  (Read 2564 times)

0 Members and 1 Guest are viewing this topic.

Offline ams_nanolab

  • Supreme QuantumATK Wizard
  • *****
  • Posts: 389
  • Country: in
  • Reputation: 11
    • View Profile
Green's function method T(E)
« on: February 10, 2017, 20:44 »
Hi,
I was wondering when we calculate the transmission spectra of a material is it with the "non-equilibrium" Green's function method? Beacuse at zero bias the system is still in equilibrium.

Should it be just

"equilibrium transmission was evaluated with  Green's function method" or

"transmission was calculated with DFT"

Because T(E) seems a fundamental quantity which helps in calculating current etc. by Landauer method.

Offline Anders Blom

  • QuantumATK Staff
  • Supreme QuantumATK Wizard
  • *****
  • Posts: 5565
  • Country: dk
  • Reputation: 93
    • View Profile
    • QuantumATK at Synopsys
Re: Green's function method T(E)
« Reply #1 on: February 10, 2017, 23:50 »
You are right that at zero bias there is only an equilibrium part of the contour integral. But at zero bias there is no current, so it's a rather uninteresting calculation. To compute any real device properties, you have to include the non-equilibrium part, at finite bias, to calculate the current. Please refer to M. Brandbyge et al., Phys. Rev. B 65, 165401 (2002) for the details.

So "the equilibrium transmission was evaluated with a Green's function method" is quite accurate, but of course at finite bias also the non-equilibrium part is computed using Green's functions. DFT is used to evaluate the Hamiltonian which goes into calculating the Green's function, but you could also use a semi-empirical Slater-Koster method, or DFTB.