Spectral properties from Matsubara Green's function approach - application to molecules

TL;DR

This paper introduces a finite-temperature Green's function method using Matsubara formalism for molecules, enabling efficient computation of quasiparticle energies and Dyson orbitals, and benchmarks second-order Coulomb interaction accuracy.

Contribution

It presents a novel approach combining Matsubara Green's functions with Gaussian basis sets for molecules, and evaluates the accuracy of second-order perturbation theory.

Findings

Accurate quasiparticle energies for small molecules.

Benchmarking of second-order Coulomb interaction accuracy.

Method suitable for time-resolved electron dynamics studies.

Abstract

We present results for many-body perturbation theory for the one-body Green's function at finite temperatures using the Matsubara formalism. Our method relies on the accurate representation of the single-particle states in standard Gaussian basis sets, allowing to efficiently compute, among other observables, quasiparticle energies and Dyson orbitals of atoms and molecules. In particular, we challenge the second-order treatment of the Coulomb interaction by benchmarking its accuracy for a well-established test set of small molecules, which includes also systems where the usual Hartree-Fock treatment encounters difficulties. We discuss different schemes how to extract quasiparticle properties and assess their range of applicability. With an accurate solution and compact representation, our method is an ideal starting point to study electron dynamics in time-resolved experiments by the propagation of the Kadanoff-Baym equations.