Light emission and finite frequency shot noise in molecular junctions: from tunneling to contact

TL;DR

This paper investigates light emission and shot noise in molecular junctions across tunneling and contact regimes, providing a theoretical framework and computational scheme that align with experimental observations.

Contribution

It introduces a practical Green's function-based method to calculate finite-frequency shot noise and light emission in molecular junctions, bridging theory and experiment.

Findings

Theoretical results match experimental light emission features.

Finite-frequency shot noise explained by inelastic electronic transitions.

Developed a computational scheme for realistic molecular structures.

Abstract

Scanning tunneling microscope induced light emission from an atomic or molecular junction has been probed from the tunneling to contact regime in recent experiments. There, the intensity of the light emission shows strong correlation with the current/charge fluctuations at optical frequencies. We show that this is consistent with the established theory in the tunneling regime, by writing the finite-frequency shot noise as a sum of inelastic transitions between different electronic states. Based on this, we develop a practical scheme to perform calculations on realistic structures using Green's functions. The photon emission yields obtained re-produce the essential feature of the experiments.