Quasiparticle Effects on Tunneling Currents: A Study ofC2H4Adsorbed on theSi(001)-(2×1)Surface

We present a first-principles calculation of the quasiparticle electronic structure of ethylene adsorbed on the dimer reconstructed $\mathrm{Si}\left(001\right)-(2\times 1)$ surface. Within the $\mathrm{GW}$ approximation, the self-energy corrections for the adsorbate states are found to be about 1.5 eV larger than those for the states derived from bulk silicon. The calculated quasiparticle band structure is in excellent agreement with photoemission spectra. Finally, the effects of the quasiparticle corrections on the scanning tunneling microscope images of the adsorbed molecules are shown to be important as the lowering of the ${\mathrm{C}}_2{\mathrm{H}}_4$ energy levels within $\mathrm{GW}$ strongly reduces their tunneling probability.