Conductance from Transmision spectrum and IV

[asma]

Dear Experts,

I'm calculating the conductance for the device I built from the transmission spectrum. Using the below code:

transmission_spectrum = nlread("Device 1.hdf5",TransmissionSpectrum)[0]
temperature_list=numpy.linspace(300,300,1)*Kelvin
conductance_list=numpy.zeros(len(temperature_list))
#calculate the conductance for room temperature
for i in range(len(temperature_list)):
    conductance_list=transmission_spectrum.conductance(
        electrode_temperatures=(temperature_list, temperature_list))

Then I calculated the IV using Analysis, but the results doesn't make sense.
As G=I/V

For example I'm getting 1.94E-10 S conductance and 3.08E-11 current when applying 0.1 bias voltage.

Please Advise

[Petr Khomyakov]

Please describe what you studied in more detail and explain why the results do not make sense.

[asma]

I'm using the z shaped device in this tutorial: https://docs.quantumwise.com/v2017/tutorials/vnl_graphene_transistor/vnl_graphene_transistor.html

I calculated the transmission spectrum for different configurations.
I need to calculate the conductance and current for different bias voltages so I'm using the below code:

transmission_spectrum = nlread("Device 1.hdf5",TransmissionSpectrum)[0]
temperature_list=numpy.linspace(300,300,1)*Kelvin
conductance_list=numpy.zeros(len(temperature_list))
current_list=numpy.zeros(len(temperature_list))
for i in range(len(temperature_list)):
    current_list=transmission_spectrum.current( electrode_temperatures=(temperature_list, temperature_list),electrode_voltages=(0.25*Volt,-0.25*Volt))
        conductance_list=transmission_spectrum.conductance( electrode_temperatures=(temperature_list, temperature_list),electrode_voltages=(0.25*Volt,-0.25*Volt))

I was getting the current from IV analysis but I was getting high conductance with low current. The relation was not direct proportion.
After using this code the results are direct proportion.
How can I be sure that my results are right?
Can I get current and conductance from same transmission spectrum at different bias voltages?

Thanks

[Petr Khomyakov]

Conductance is the derivative of the current with respect to the bias voltage applied, i.e., G = dI/dV. It means that even when the current is zero, e.g., at V=0, conductance has a finite value. So, I do not understand your concern regarding low current vs. high conductance - it is like comparing apples with oranges. Small values for a given quantity do not mean immediately that the derivative values of that quantity are small.

Regarding calculating the current from the transmission spectrum obtained at zero-bias voltage, 0 V. You can do it indeed - this is called linear response approximation. It is valid for some systems voltage ranges, but it may fail for the others. In the latter case, you have to calculate the current in a self-consistent manner for each bias point. Whether linear response approximation holds for your system of study, I do not know, and that is something you should investigate.