Quasiparticle Electronic Structures

Abstract

The energy positions of the main peaks in the spectral functions of inhomogeneous electron gases represent their quasiparticle electronic structures. Discussing numerical results based on ab initio Kohn-Sham and generalized Kohn-Sham starting electronic structures the great success of the Hedin GW approximation to the exchange-correlation energy is demonstrated for condensed matter in general. A central result for semiconductors and insulators is the calculation of energy gaps but also bands and their dispersion in reasonable agreement with experimental data. Of course, the obtained quasiparticle energies depend slightly on computational details such as starting point, self-consistency, convergence, and inclusion of vertex corrections beyond the GW approximation. Nevertheless, the resulting global or projected densities of states are applicable to explain spectra measured by means of various spectroscopies. Basically the conclusions derived for non-metals remain valid for bulk metallic and magnetic systems. The great success of the quasiparticle description is also shown for molecules and other low-dimensional systems with confinement of electrons in three, two or one directions.