Quasiparticle wavefunction and its equation of motion

TL;DR

This paper introduces a new definition of the quasiparticle wavefunction derived from Green functions, which accounts for decay and coupling to collective excitations, leading to a simplified equation of motion.

Contribution

A novel quasiparticle wavefunction concept derived from Green functions that includes decay and collective effects, with a new equation of motion in the dynamical exchange-correlation framework.

Findings

The new quasiparticle wavefunction contains multiple modes due to collective coupling.

A simplified equation of motion with an effective field is derived.

A model for the effective potential suitable for electron-gas-like materials is proposed.

Abstract

The quasiparticle wavefunction of a many-electron system is traditionally defined as the eigenfunction of the quasiparticle eigenvalue equation involving the self-energy. In this article a new concept of a quasiparticle wavefunction is derived from the general definition of the Green function without reference to self-energy. The proposed quasiparticle wavefunction can decay in time, and in contrast to the traditional one it contains not only the main quasiparticle mode but also other modes due to coupling to collective excitations in the system. In the recently developed dynamical exchange-correlation potential formalism, the new definition of a quasiparticle wavefunction leads to an equation of motion with an effective field, which appears to have a simple form expected to be amenable to realistic approximations. A simple model for the effective potential is proposed, which is suitable for electron-gas-like materials such as the alkali.