Towards Noise Simulation in Interacting Nonequilibrium Systems Strongly Coupled to Baths

TL;DR

This paper introduces a computational approach using nonequilibrium Hubbard Green functions to simulate noise in interacting nanoscale systems, bridging the gap between weak and strong coupling regimes with broad applicability.

Contribution

The paper presents a novel, cost-effective method for noise evaluation in first principles simulations applicable across various interaction strengths.

Findings

The approach accurately reproduces known noise spectra in benchmark models.

Simulations demonstrate effectiveness across weak, intermediate, and strong interaction regimes.

Comparison with exact data validates the method's reliability.

Abstract

Progress in experimental techniques at nanoscale made measurements of noise in molecular junctions possible. These data are important source of information not accessible through average flux measurements. Emergence of optoelectronics, recently shown possibility of strong light-matter couplings, and developments in the field of quantum thermodynamics are making counting statistics measurements of even higher importance. Theoretical methods for noise evaluation in first principles simulations can be roughly divided into approaches applicable in the case of weak intra-system interactions, and those treating strong interactions for systems weakly coupled to baths. We argue that due to structure of its diagrammatic expansion and the fact of utilizing many-body states as a basis of its formulation recently introduced nonequilibrium Hubbard Green functions formulation is a relatively inexpensive method suitable for evaluation of noise characteristics in first principles simulations over wide range of parameters. We illustrate viability of the approach by simulations of noise and noise spectrum within generic models for non-, weakly and strongly interacting systems. Results of the simulations are compared to exact data (where available) and to simulations performed within approaches best suited for each of the three parameter regimes.