Evolution of shot noise in suspended lithographic gold break junctions with bias and temperature

Shot noise is a powerful tool to probe correlations and microscopic transport details that conductance measurements alone cannot reveal. Even in atomic-scale Au devices that are well described by Landauer–Büttiker physics, complications remain such as local heating and electron–phonon interactions. We report systematic rf measurements of shot noise in individual atomic-scale gold break junctions at multiple temperatures, with most bias voltages well above the energy of the Au optical phonon mode. Motivated by the previous experimental evidence that electron–phonon interactions can modify Fano factors and result in kinked features in bias dependence of shot noise, we find that the temperature dependence of shot noise from 4.2 to 100 K is minimal. Enhanced Fano factors near $0.5G_0$ and features beyond simply linear bias dependence of shot noise near the $1G_0$ plateau are observed. Both are believed to have non-interacting origins and the latter likely results from slightly bias-dependent transmittance of the dominant quantum channel. (paper)