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I am looking for the electron transport study in a single gold atom, like the system of single carbon atom shown in transiesta paper by Nick Papior et al. Computer Physics Communications, 212, 8-24, (2017).

I have connected the gold atom with linear chains of silver atoms, and has studied the effect of symmetric variation of Ag-Au separation. (Figure attached here)

I am getting transmission peaks at energy slightly below the 4eV, while there is no energy level in the discrete levels of single gold, and the PDOS plot. Moreover, the position of a peak near the Fermi level is not consistent with the position of the discrete system.

To mention these calculations are done for zero bias, so in principle, resonant tunneling is expected.

Also, as a result of increasing Ag-Au separation, there is more suppression of transmission in some channels, while some attain the same height. Last subplot show discrete levels of gold atom.

I have these queries:

(a) Why is transiesta giving the peaks where there is no energy level?

(b) Is the separation in peaks here describe the weak Ag-Au coupling?

Thanks in advance. electron transport in a single gold atom, black line for up-spin and red line for down-spin channels. Last subplot show discrete levels of gold atom

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With a single atom there might be leakage current. Probably, if you had more Au atoms the transmission would be fully suppressed.

The 4 eV peak is likely close to a van-Hove singularity of the electrode chains and hence the DOS goes to infinity. So any small(tiny) transmission probability will show it self when the DOS is exceedingly large.

You can clearly see that the longer separation yields a narrower Lorentizian meaning that you are very weakly coupling the single-atom.

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  • $\begingroup$ As there is not 1-1 correspondence, how can we justify the peaks according to the discrete levels of dot. $\endgroup$
    – sushil
    May 10, 2022 at 9:28
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    $\begingroup$ That is your responsibility to figure out. When the atoms are in the chain, it stops being a "lone dot" and you'll have to figure out how the energy levels re-align based on the electrode couplings. Transmission peaks are a result of incoming waves (if there are no incoming waves, no electrons can travel through the system) + the transmission probability (here depending on the dot). $\endgroup$
    – nickpapior
    May 10, 2022 at 9:31
  • $\begingroup$ Thanks for your suggestion sir. $\endgroup$
    – sushil
    May 10, 2022 at 9:38

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