Electron-plasmon and electron-phonon satellites in the angle-resolved photoelectron spectra of n-doped anatase TiO2

TL;DR

This paper presents a first-principles method to analyze electron-plasmon and electron-phonon interactions in doped semiconductors, applied to TiO2, revealing the significant role of plasmons in spectral features and their dependence on carrier concentration.

Contribution

The study introduces a comprehensive first-principles approach to simultaneously evaluate electron-plasmon and electron-phonon effects on photoemission spectra in doped materials.

Findings

Electron-plasmon coupling creates satellite features similar to polarons.

Plasmon energies and spectral signatures vary with carrier concentration.

Electron-plasmon interactions contribute around 40% to the total electron-boson coupling.

Abstract

We develop a first-principles approach based on many-body perturbation theory to investigate the effects of the interaction between electrons and carrier plasmons on the electronic properties of highly-doped semiconductors and oxides. Through the evaluation of the electron self-energy, we account simultaneously for electron-plasmon and electron-phonon coupling in theoretical calculations of angle-resolved photoemission spectra, electron linewidths, and relaxation times. We apply this methodology to electron-doped anatase TiO2 as an illustrative example. The simulated spectra indicate that electron-plasmon coupling in TiO2 underpins the formation of satellites at energies comparable to those of polaronic spectral features. At variance with phonons, however, the energy of plasmons and their spectral fingerprints depends strongly on the carrier concentration, revealing a complex interplay between plasmon and phonon satellites. The electron-plasmon interaction accounts for approximately 40% of the total electron-boson interaction strength and it is key to improve the agreement with measured quasiparticle spectra.