# Local-noise spectroscopy for non-equilibrium systems

## TL;DR

Local-noise spectroscopy (LNS) is a theoretical tool for analyzing non-equilibrium systems through flux density correlations, offering insights into microscopic properties, interactions, and thermal characteristics, especially in biased molecular junctions.

## Contribution

This paper introduces the concept and theoretical framework of local-noise spectroscopy, extending flux-based methods to provide detailed local information in non-equilibrium systems.

## Key findings

- LNS can reveal microscopic properties of bias-induced light emission.
- LNS provides local resolution of intra-system interactions.
- LNS can serve as a nano-thermometry tool.

## Abstract

We introduce the notion, and develop the theory of local-noise spectroscopy (LNS) - a tool to study the properties of systems far from equilibrium by means of flux density correlations. As a test bed, we apply it to biased molecular junctions. This tool naturally extends those based on local fluxes, while providing complementary information on the system. As examples of the rich phenomenology that one can study with this approach, we show that LNS can be used to yield information on microscopic properties of bias-induced light emission in junctions, provide local resolution of intra-system interactions, and employed as a nano-thermometry tool. Although LNS may, at the moment, be difficult to realize experimentally, it can nonetheless be used as a powerful theoretical tool to infer a wide range of physical properties on a variety of systems of present interest.