Photoemission spectroscopy from the three-body Green's function.

We present an original approach for the calculation of direct and inverse photo-emission 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.

Our method uses as a key quantity the three-body Green's function, or, more precisely, its hole-hole-electron and electron-electron-hole parts.

We show that, contrary to the one-body Green's function, satellites are already present in the corresponding non-interacting 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 also show how the one-body Green's function can be retrieved from the three-body Green's function.

We illustrate our approach by applying it to the symmetric Hubbard dimer.