Transmission Spectrum

[PJ]

Hi,
Can anyone please explain me what is the formula by which transmission spectrum is converted to conductance at zero bias. I have searched it on internet, but I could not found it. I found the conductance using Transmission spectrum from analyzer, and I got two conductance, one G0 which is a straight line and one at the bottom, which is an integer value.
Please explain me for the same. I have also attached the TS curve with this query.

[kstokbro]

At T=0, the conductance in units of G0 is given by the transmission coefficient at the Fermi level.

You system has a conductance of 0.000125 G0 (upper figure), corresponding to T(0)=0.000125 (lower figure).

For T>0 the conductance is averaged with the derivative of the fermi function, 
see forinstance  Phys Rev. B 79, 205322 (2009)
however, this is an unimportant detail for your system.

[PJ]

A very thanks for your reply. I am still not clear that you have written that at T=0, the conductance in units of G0 is given by the transmission coefficient at the Fermi level.  But I have calculated all the results at NO BIAS, i.e. I have not applied any voltage, so does it mean the same (i.e at T=0).
And without applying any voltage, how we get a transmission curve, as electron can only move from left to right in the presence of voltage.
And why we take transmission coefficient at the Fermi level.

[Anders Blom]

Conductance is the quantum ballistic version of resistance. Even if you don't apply any voltage to a copper wire, it still has a specific resistance. Same with conductance. We can estimate the low-bias conductance from the zero bias transmission spectrum, although in principle it should be computed from dI/dV where V goes to zero (at least the differential conductance). But assuming it's linear at small bias, you can use the expression mentioned above.