On the initial stage of quasiparticle decay

TL;DR

This paper investigates the early nonexponential decay of quasiparticles in Fermi liquids, revealing it is governed by the zeroth spectral moment of the self-energy and proposing a simple numerical method for large systems.

Contribution

It introduces a new understanding of initial quasiparticle decay dynamics and presents a computational approach for large system analysis.

Findings

Initial decay is nonexponential and governed by the spectral moment.

Comparison with exact calculations validates the approximations.

A simple numerical method for large systems is proposed.

Abstract

The initial stages of the quasiparticle decay in a Fermi liquid are governed by a time-scale distinct from the scattering rates as derived from the Fermi golden rule approach. We show that the initial decay is nonexponential and that it is determined by the zeroth spectral moment of the electron self-energy. We analyzed numerically a number of approximations for the self-energy by comparing with exact configuration interaction calculations for small finite system with fragmented states. A numerically simple approach for computing the spreading of the quasiparticle states for large systems is devised.