Coherence and de-coherence in the Time-Resolved ARPES of realistic materials: an ab-initio perspective

TL;DR

This paper investigates the fundamental processes of coherence and de-coherence in time-resolved ARPES experiments on realistic materials, emphasizing the role of many-body interactions and ab-initio modeling.

Contribution

It provides an ab-initio perspective on the dynamics of coherence and de-coherence post photo-excitation, highlighting the complex interplay of electron-electron and electron-phonon interactions.

Findings

Coherence and de-coherence dynamics are driven by many-body correlation effects.

Electron-electron and electron-phonon scattering processes significantly influence the system's evolution.

The study offers insights into the challenges of describing photo-excited systems with simple population models.

Abstract

Coherence and de-coherence are the most fundamental steps that follow the initial photo-excitation occurring in typical Pump&Probe experiments. Indeed, the initial external laser pulse transfers coherence to the system in terms of creation of multiple electron-hole pairs excitation. The excitation concurs both to the creation of a finite carriers density and to the appearance of induced electromagnetic fields. The two effects, to a very first approximation, can be connected to the simple concepts of populations and oscillations. The dynamics of the system following the initial photo-excitation is, thus, entirely dictated by the interplay between coherence and de-coherence. This interplay and the de-coherence process itself, is due to the correlation effects stimulated by the photo-excitation. Single-particle, like the electron-phonon, and two-particles, like the electron-electron, scattering processes induce a complex dynamics of the electrons that, in turn, makes the description of the correlated and photo-excited system in terms of pure excitonic and/or carriers populations challenging.