Shot noise variation within ensembles of gold atomic break junctions at room temperature

TL;DR

This study investigates shot noise variations in gold atomic break junctions at room temperature, revealing suppression near fully transmitting channels and multiple channel participation in tunneling, influenced by surface contamination and disorder.

Contribution

It introduces a comprehensive analysis of shot noise across ensembles of atomic junctions at ambient conditions, combining experimental data with advanced simulations to understand noise behavior.

Findings

Shot noise variation is suppressed near fully transmitting channels.

Multiple channels participate in the tunneling regime.

Surface contamination and electrode disorder influence noise characteristics.

Abstract

Atomic-scale junctions are a powerful tool to study quantum transport, and are frequently examined through the mechanically controllable break junction technique (MCBJ). The junction-to-junction variation of atomic configurations often leads to a statistical approach, with ensemble-averaged properties providing access to the relevant physics. However, the full ensemble contains considerable additional information. We report a new analysis of shot noise over entire ensembles of junction configurations using scanning tunneling microscope (STM)-style gold break junctions at room temperature in ambient conditions, and compare this data with simulations based on molecular dynamics (MD), a sophisticated tight-binding model, and nonequilibrium Green's functions. The experimental data show a suppression in the variation of the noise near conductances dominated by fully transmitting channels, and a surprising participation of multiple channels in the nominal tunneling regime. Comparison with the simulations, which agree well with published work at low temperatures and ultrahigh vacuum (UHV) conditions, suggests that these effects likely result from surface contamination and disorder in the electrodes. We propose additional experiments that can distinguish the relative contributions of these factors.