Shot Noise in Nanoscale Conductors From First Principles

TL;DR

This paper presents a first-principles, field-theoretic method to calculate quantum shot noise in nanoscale conductors, revealing nonlinear and oscillatory behaviors depending on wire length and bias.

Contribution

It introduces a novel approach combining density functional theory with quantum field theory to analyze shot noise in atomic-scale conductors.

Findings

Shot noise is strongly nonlinear with bias in atomic wires.

Shot noise is enhanced in short wires due to electrode contributions.

Longer wires exhibit oscillatory shot noise behavior related to atomic structure.

Abstract

We describe a field-theoretic approach to calculate quantum shot noise in nanoscale conductors from first principles. Our starting point is the second-quantization field operator to calculate shot noise in terms of single quasi-particle wavefunctions obtained self-consistently within density functional theory. The approach is valid in both linear and nonlinear response and is particularly suitable in studying shot noise in atomic-scale conductors. As an example we study shot noise in Si atomic wires between metal electrodes. We find that shot noise is strongly nonlinear as a function of bias and it is enhanced for one- and two-Si wires due to the large contribution from the metal electrodes. For longer wires it shows an oscillatory behavior for even and odd number of atoms with opposite trend with respect to the conductance, indicating that current fluctuations persist with increasing wire length.