Quantum Monte Carlo method for models of molecular nanodevices

TL;DR

This paper presents a quantum Monte Carlo method for accurately calculating Green functions at finite temperatures in models of molecular nanodevices, specifically applied to the Anderson-Holstein model.

Contribution

A new quantum Monte Carlo algorithm is introduced for impurity models coupled to bosonic fields, demonstrating high accuracy and efficiency in molecular transistor simulations.

Findings

The method accurately computes the density of states across various parameters.

Conductance behavior consistent with Kondo physics observed even with strong phonon attraction.

The approach is versatile for different impurity-boson coupling regimes.

Abstract

We introduce a quantum Monte Carlo technique to calculate exactly at finite temperatures the Green function of a fermionic quantum impurity coupled to a bosonic field. While the algorithm is general, we focus on the single impurity Anderson model coupled to a Holstein phonon as a schematic model for a molecular transistor. We compute the density of states at the impurity in a large range of parameters, to demonstrate the accuracy and efficiency of the method. We also obtain the conductance of the impurity model and analyze different regimes. The results show that even in the case when the effective attractive phonon interaction is larger than the Coulomb repulsion, a Kondo-like conductance behavior might be observed.