AB-G$_0$W$_0$: A practical G$_0$W$_0$ method without frequency integration based on an auxiliary boson expansion

Abstract: Common G$_0$W$_0$ implementations rely on numerical or analytical frequency integration to determine the G$_0$W$_0$ self-energy, which results in a variety of practical complications. Recently, we demonstrated an exact connection between the G$_0$W$_0$ approximation and equation-of-motion (EOM) quantum chemistry approaches [J. Chem. Phys., 158, 124123 (2023)]. Based on this connection, we propose a new method to determine G$_0$W$_0$ quasiparticle energies which completely avoids frequency integration and its associated problems. To achieve this, we make use of an auxiliary boson (AB) expansion. We name the new approach AB-G$_0$W$_0$ and demonstrate its practical applicability in a range of molecular problems.