QuantumATK Forum

QuantumATK => General Questions and Answers => Topic started by: cinda on July 2, 2012, 07:44

Title: Conductance
Post by: cinda on July 2, 2012, 07:44

Dear all,
I read the manual, and the conductance used the expression G=T(E_F)G₀. And I know the transmission coefficient is given by T(E,ΔV)=4Tr[Im(∑^l_l,l)G^R_l,rIm(∑^r_r,r)G^A_r,l]
I calculate the transmission coefficient with no gate voltage and bias voltage, so I can obtain the transmission coefficient at fermi energy. And then I used the G=T(E_F)G₀ obtain the conductance. But I have questions, if I did not used the voltage, how could T(E,ΔV) obtain? what value is the ΔV set up?
Thanks~

Title: Re: Conductance
Post by: Nordland on July 2, 2012, 13:54

If you use the method called conductance() on the TransmissionSpectrum all of this is carried out for you automatically.

Title: Re: Conductance
Post by: cinda on July 4, 2012, 05:09

I realize that in the method is automatically, but I want to known if there is no gate voltage and bias voltage how did you known the conductance?
Because the conductance is I/V, if we don't apply the voltage where is the conductance come from?

Title: Re: Conductance
Post by: kstokbro on July 4, 2012, 12:55

It is the linear response conductance, i.e. I/V  in the limit V -> 0

Title: Re: Conductance
Post by: Anders Blom on July 4, 2012, 15:54

... which you can easily prove analytically is T(E_F)G₀, as you wrote in the beginning, cinda :)

Title: Re: Conductance
Post by: cinda on July 5, 2012, 06:27

Thank you very much!! I get the point.

Title: Re: Conductance
Post by: PJ on June 20, 2013, 11:24

can any one explain me how is it possible to get conductance without the application of Voltage and what is the difference between G and G0.

Title: Re: Conductance
Post by: Anders Blom on July 21, 2013, 23:45

Conductance is a material parameter, like resistance. You don't need a voltage to have a resistance. Same with conductance.

G is typically the symbol for conductance. G0 is the conductance quantum (http://en.wikipedia.org/wiki/Conductance_quantum).