Quasiparticle Self-consistent GW Approximation as a Universal Framework for Electronic Structure

A new type of self-consistent scheme within the GW approximation is presented, which we call the quasiparticle self-consistent GW (QSGW ) approxi- mation. It is based on a kind of self-consistent perturbation theory, where the self-consistency is used to minimize the difference between the many-body and single-particle hamiltonians. QSGW describes optical properties in a wide range of materials rather well, including cases where the local-density and LDA-based GW approximations fail qualitatively. Self-consistency dramatically improves agreement with experiment, and is sometimes essential. QSGW avoids some formal and practical problems encountered in conventional self-consistent GW, which will be discussed. It handles both itinerant and correlated electrons on an equal footing, without any ambiguity about how a localized state is defined, or how double-counting terms should be subtracted. Weakly correlated materials such as Na and sp semiconductors are described with uniformly high accuracy. Discrepancies with experiment are small and systematic, and can be explained in terms of the approximations made.

Its consistently high accuracy make QSGW a versatile method that can reliably predict critical energy band properties of graphene, CuInSe2, CaFe2As2 and NiO in a unified framework. Many other properties attendant to the electronic structure can be calculated, such as magnetic excitations, the Auger recombination process, the transmission through a metal-semiconductor contact. In principle it can serve both as a framework to construct effective hamiltonians for many-body physics, and as an engine to build models for device design from first principles, with unprecedented reliability. How to do this in practice is a major challenge today. I will briefly present some discussion of each.