Photoemission spectral functions from the three-body Green's function

We present an original strategy for the calculation of direct and inverse photoemission spectra from first principles. The main goal is to go beyond the standard Green's function approaches, such as the GW method, in order to find a good description not only of the quasiparticles but also of the satellite structures, which are of particular importance in strongly correlated materials. To this end we use as a key quantity the three-body Green's function, or, more precisely, its hole-hole-electron and electron-electron-hole parts, and we show how the one-body Green's function, and hence the corresponding spectral function, can be retrieved from it. We show that, contrary to the one-body Green's function, information about satellites is already present in the non-interacting three-body Green's function. Therefore, simple approximations to the three-body self-energy, which is defined by the Dyson equation for the three-body Green's function and which contains many-body effects, can still yield accurate spectral functions. In particular, the self-energy can be chosen to be static which could simplify a self-consistent solution of the Dyson equation. We give a proof of principle of our strategy by applying it to the Hubbard dimer, for which the exact self-energy is available. (C) Copyright G. Riva et al.

Automated summary

This article presents an original strategy for calculating direct and inverse photoemission spectra from first principles. The main goal is to go beyond standard Green's function approaches and accurately describe both quasiparticles and satellite structures in strongly correlated materials. The authors use the three-body Green's function as a key quantity and demonstrate how to retrieve the one-body Green's function from it. They also find that satellite information is already present in the non-interacting three-body Green's function and that simple approximations to the three-body self-energy can yield accurate spectral functions.