Real-time coupled-cluster approach for the cumulant Green's function

• Published in: arXiv.org
• Main Authors: Vila, F D, Rehr, J J, Kas, J J, Kowalski, K, Peng, B
• Format: Paper Journal Article
• Language: English
• Published: Ithaca Cornell University Library, arXiv.org 12.06.2020
• Subjects: Clusters; Differential equations; Equations of motion; Green's functions; Nonlinear equations; Perturbation theory; Photoelectric emission; Physics - Chemical Physics
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2006.07477

Green's function methods within many-body perturbation theory provide a general framework for treating electronic correlations in excited states. Here we investigate the cumulant form of the one-electron Green's function based on the coupled-cluster equation of motion approach in an extension of our previous study. The approach yields a non-perturbative expression for the cumulant in terms of the solution to a set of coupled first order, non-linear differential equations. The method thereby adds non-linear corrections to traditional cumulant methods linear in the self energy. The approach is applied to the core-hole Green's function and illustrated for a number of small molecular systems. For these systems we find that the non-linear contributions lead to significant improvements both for quasiparticle properties such as core-level binding energies, as well as the satellites corresponding to inelastic losses observed in photoemission spectra.