Understanding the Electronic Transport Through Single Noble Gas Atoms
  We present a theoretical study of the conductance of atomic junctions comprising single noble gas atoms (He, Ne, Ar, Kr, and Xe) coupled to gold electrodes. The aim is to elucidate how the presence of noble gas atoms affects the electronic transport through metallic atomic-size contacts. Our analysis, based on density functional theory and including van der Waals interactions, shows that for the lightest elements (He and Ne) no significant current flows through the noble gas atoms and their effect is to reduce the conductance of the junctions by screening the interaction between the gold electrodes. This explains the observations reported in metallic atomic-size contacts with adsorbed He atoms. Conversely, the heaviest atoms (Kr and Xe) increase the conductance due to the additional current path provided by their valence p states. 
L. A. Zotti, M. B\"urkle, Y. J. Dappe, F. Pauly, and J. C. Cuevas
cond-mat.mes-hall cond-mat.mtrl-sci