Elementary Excitations I: Single Electronic Quasiparticles

Abstract

Surfaces are many-body systems consisting of interacting cores and electrons (Sect. 3.3.1). In order to describe many properties, in particular, groundstate properties, it is sufficient to replace the system of interacting electrons by a system of independent particles (3.2). One example is the density functional theory (Sect. 3.4.1) within the local approximation for the exchange and correlation contribution to the total energy (3.50). Using the Kohn-Sham equation (3.46), the ground state of the electronic subsystem can be described by independent (i.e., effectively non-interacting) particles, more strictly electrons moving in an effective single-particle potential (3.48). An ‘independent’ electron in a Kohn-Sham state possesses a fixed single-particle energy and a defined probability distribution of finding this electron in space. However, excitations of an electronic system cannot correctly be described by the independent Kohn-Sham particles in (3.46).