Inelastic Current Noise in Nanoscale Systems: Scattering Theory Analysis

TL;DR

This paper develops a scattering theory framework to analyze inelastic current noise in nanoscale systems with electron-vibration interactions, explaining how elastic and inelastic processes influence shot noise and its voltage derivatives.

Contribution

It introduces a detailed scattering theory approach to distinguish elastic and inelastic contributions to shot noise in nanoscale conductors, relating these to experimental observations.

Findings

Identification of transmission ranges with sign crossover in inelastic noise signals.

Bounds on inelastic noise ratios based on vibrational mode symmetry.

Theoretical justification for recent experimental and numerical results.

Abstract

We present a scattering theory description for the inelastic current noise in the presence of electron-vibration interactions. In this description, we specify elastic and inelastic scattering contributions to the shot noise by examining charge transfers between scattering states and energy exchange between electrons and vibrations. The elastic and inelastic scattering processes are further decomposed into current correlations of electrons at the same energy and those of electrons at different energies. Focusing on the inelastic noise signals defined as steps in the voltage derivative of the shot noise, we show that single-channel systems have two ranges of transmission at which the inelastic noise signals exhibit the crossover between positive and negative signs. In a high transmission regime, even and odd vibrational modes of mirror-symmetric systems provide upper and lower bounds to the ratio of the inelastic noise signal to the conductance step. This can be a theoretical justification for models used to understand the recent noise experiment [Phys. Rev. Lett. 108, 146602 (2012)] and numerical calculations on gold atomic chains [Phys. Rev. B 86, 155411 (2012)].