jp9b06766_si_001.pdf (1.05 MB)
Origin of the Anomalous Electronic Shot Noise in Atomic-Scale Junctions
journal contribution
posted on 2019-09-20, 14:46 authored by Anqi Mu, Ofir Shein-Lumbroso, Oren Tal, Dvira SegalFluctuations
pose fundamental limitations in making sensitive measurements,
yet at the same time, noise unravels properties that are inaccessible
at the level of the averaged signal. In electronic devices, shot noise
arises from the discrete nature of charge carriers, and it increases
linearly with averaged current (or applied bias for ohmic conductors)
according to the celebrated Schottky formula. Nonetheless, measurements
of shot noise in atomic-scale junctions at high voltage reveal significant
nonlinear (anomalous) behavior, which varies from sample to sample,
and has no specific trend. Here, we provide a viable, unifying explanation
for these diverse observations based on the theory of quantum coherent
transport. Our formula for the anomalous shot noise relies onand
allows us to resolvetwo key characteristics of a conducting
junction: The structure of the transmission function at the vicinity
of the Fermi energy and the asymmetry of the bias voltage drop at
the contacts. We test our theory on high voltage shot noise measurements
on Au atomic scale junctions and demonstrate a quantitative agreement,
recovering both the enhancement and suppression of shot noise as observed
in different junctions. The good theory–experiment correspondence
supports our modeling and emphasizes that the asymmetry of the bias
drop on the contacts is a key factor in nanoscale electronic transport,
which may substantially impact electronic signals even in incomplex
structures.