Real-time coupled-cluster approach for the cumulant Green's function
Fernando Vila
John Rehr
Joshua Kas
Karol Kowalski
Bo Peng
Abstract
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.
Revised: November 17, 2020 |
Published: November 10, 2020