Quasiparticle spectra from molecules to bulk

TL;DR

This paper introduces a stochastic cumulant GW method to analyze how photoemission spectra, quasiparticle energies, and collective excitations evolve from molecules to bulk materials, revealing size-independent spectral features.

Contribution

The paper presents a novel stochastic cumulant GW approach capable of studying large systems from molecules to bulk, capturing quasiparticle and collective excitation evolution.

Findings

Quasiparticle energies increase due to coupling with plasmon excitations.

Spectral weight loss of up to 50% observed in low energy states.

Collective excitations and their effects are consistent across different system sizes.

Abstract

A stochastic cumulant GW method is presented, allowing us to map the evolution of photoemission spectra, quasiparticle energies, lifetimes and emergence of collective excitations from molecules to bulk-like systems with up to thousands of valence electrons, including Si nanocrystals and nanoplatelet. The quasiparticle energies rise due to their coupling with collective shake-up (plasmon) excitations, and this coupling leads to significant spectral weight loss (up to 50% for the low energy states), shortening the lifetimes and shifting the spectral features to lower energy by as much as 0.6 eV. Such features are common to all the systems studied irrespective of their size and shape. For small and low dimensional systems the surface plasmon resonances affect the frequency of the collective excitation and position of the satellites.