Photoemission Signatures of Non-Equilibrium Carrier Dynamics from First Principles

TL;DR

This paper introduces a first-principles Green's function approach to predict time-resolved photoemission spectra, revealing the non-equilibrium carrier thermalization process in graphene and identifying hot-phonon effects.

Contribution

It develops a novel first-principles formalism for interpreting tr-ARPES data and clarifies the mechanisms of carrier thermalization in graphene.

Findings

Excellent agreement with experimental spectra for graphene.

Identification of hot-phonon regime as dominant in non-equilibrium dynamics.

First-principles prediction of carrier relaxation timescales.

Abstract

Time- and angle-resolved photoemission spectroscopy (tr-ARPES) constitutes a powerful tool to inspect the dynamics and thermalization of hot carriers. The identification of the processes that drive the dynamics, however, is challenging even for the simplest systems owing to the coexistence of several relaxation mechanisms. Here, we devise a Green's function formalism for predicting the tr-ARPES spectral function and establish the origin of carrier thermalization entirely from first principles. The predictive power of this approach is demonstrated by an excellent agreement with experiments for graphene over time scales ranging from a few tens of femtoseconds up to several picoseconds. Our work provides compelling evidence of a non-equilibrium dynamics dominated by the establishment of a hot-phonon regime.