Towards Noise Simulation in Interacting Nonequilibrium Systems Strongly Coupled to Baths

Abstract

Progress in experimental techniques at nanoscale makes measurements of noise in molecular junctions possible. These data are important source of information not accessible through average flux measurements. The emergence of optoelectronics, the recently shown possibility of strong light-matter couplings, and developments in the field of quantum thermodynamics are making measurements of transport statistics even more important. Theoretical methods for noise evaluation in first principles simulations can be roughly divided into approaches for 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 use of many-body states as a basis of its formulation, the recently introduced nonequilibrium diagrammatic technique for Hubbard Green functions is a relatively inexpensive method suitable for evaluation of noise characteristics in first principles simulations over a 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.

Many-Body State Description of Single-Molecule Electroluminescence Driven by a Scanning Tunneling Microscope

“…The Hubbard NEGF, recently introduced by us, was shown to be superior relative to the PP-NEGF at low orders of diagrammatic expansion. 50 Here we utilize the Hubbard NEGF for description of transport and optical response in a single molecule junction. Experimental techniques involving a scanning tunneling microscope (STM) have been widely used to observe atomically resolved surface topography and to investigate the local density of states, thus providing information on the molecular electronic structure.…”

Electron Traversal Times in Disordered Graphene Nanoribbons

“…Even though our approach is limited to noninteracting electrons, we expect the current correlations and traversal times to be similarly related even when dealing with, e.g., electron–electron or electron–phonon interactions [ 47 , 73 , 74 , 75 ]. If perturbation theory could be applied, i.e., when the interaction is weak, current correlation or noise simulations are still feasible to perform in terms of the one-particle Green’s function [ 76 , 77 , 78 , 79 , 80 , 81 ]. Disordered interacting systems have also been studied using mean-field or density-functional theories [ 82 , 83 , 84 ].…”

Electron Transfer Methods in Open Systems

“…Thus, perturbative expansion in the system-baths couplings in each order yields product of two multi-time correlation functions: one for the system and one for the . The technique appears to be quite stable over wide range of parameters, 69 helpful in evaluation of electronic friction in junctions, 70,71 and useful as a convenient tool in first principles simulations of optoelectronic devices. [56][57][58] It is important to realize, however, that requirement of equilibrium character of the…”