Structure and conductance histogram of atomic-sized Au contacts

Abstract

Many experiments have shown that the conductance histograms of metallic atomic-sized contacts exhibit a peak structure, which is characteristic of the corresponding material. The origin of these peaks still remains as an open problem. In order to shed some light on this issue, we present a theoretical analysis of the conductance histograms of Au atomic contacts. We have combined classical molecular dynamics simulations of the breaking of nanocontacts with conductance calculations based on a tight-binding model. This combination gives us access to crucial information such as contact geometries, forces, minimum cross-section, total conductance and transmission coefficients of the individual conduction channels. The ensemble of our results suggests that the low temperature Au conductance histograms are a consequence of a subtle interplay between mechanical and electrical properties of these nanocontacts. At variance with other suggestions in the literature, our results indicate that the peaks in the Au conductance histograms are not a simple consequence of conductance quantization or the existence of exceptionally stable radii. We show that the main peak in the histogram close to one quantum of conductance is due to the formation of single-atom contacts and chains of gold atoms. Moreover, we present a detailed comparison with experimental results on Au atomic contacts where the individual channel transmissions have been determined.

Heat transport through atomic contacts

“…Then the ratio TH,ph / TH,el will be constant with the electrical conductance. For contacts of very few conductance channels this does not hold strictly, because the correspondence of the cross sectional area of one atom to one conduction channel is valid only for the single atom case 20 . Nevertheless, the range TH,ph = (0.02 ÷ 0.22) TH,el from the above considerations should account for these uncertainties and approximations.…”

“…Owing to 1D confinement of electrons, spin-charge separation occurs, enabling scattering mechanisms to affect charge and heat transport independently. It has been experimentally demonstrated recently that isolated monoatomic gold chains on surfaces host such a Tomonaga-Luttinger liquid state 20 . Although atomic junctions are well described by the Fermi-liquid theory, no experimental demonstration on the validity of WF at this scale has so far been reported.…”

“…Verification of the WF law for metallic nanostructures, however, has proved to be difficult. 20 . Although atomic junctions are well described by the Fermi-liquid theory, no experimental demonstration on the validity of WF at this scale has so far been reported.…”

Ballistic resistivity in aluminum nanocontacts

“…Note that the presence of some conductance traces with slow conductance decays at the last stage of the nanowire breakage ͑as those shown in peaked structure at higher conductance values. We recall that a peaked structure has also been observed in minimum crosssection histograms, 15,23 reflecting the existence of energetically favorable atomic configurations at the nanocontact neck.…”

“…22 The results reveal a statistically linear relationship between the conductance and the number of aluminum atoms contact. A similar strategy has been recently proposed 23 for constructing computational gold conductance histograms, although a parametrized tight-binding approach has been used to calculate conductance values.…”