Dynamical effects in electron spectroscopy.

Area of Science:

• Condensed-matter physics
• Theoretical physics
• Quantum mechanics

Background:

• Describing Coulomb interaction effects on material properties is a major challenge.
• The GW approximation often fails to accurately predict satellite spectra.
• Dynamical effects, like plasmon satellites, require advanced theoretical approaches.

Purpose of the Study:

• To provide a unified derivation of the GW approximation and cumulant expansion for the one-body Green's function.
• To compare spectral functions and discuss quasi-particle/satellite dispersion using bulk sodium as a model.
• To investigate the importance of self-consistency and experimental corrections for accurate spectral function predictions.

Main Methods:

• Unified derivation of GW approximation and cumulant expansion.
• Calculation and comparison of spectral functions for bulk sodium (valence and core regions).
• Analysis of quasi-particle and satellite dispersion, including self-consistency effects.

Main Results:

• Demonstrated the crucial role of self-consistency for accurate results, especially at large binding energies.
• Achieved excellent agreement with experimental data after correcting spectral functions for extrinsic and interference effects.
• Successfully compared the GW approximation and cumulant expansion for describing spectral functions and satellites.

Conclusions:

• The unified approach provides a robust framework for understanding electron-boson coupling and spectral features.
• Self-consistency and experimental effect corrections are vital for reliable predictions in condensed-matter spectroscopy.
• The study lays groundwork for analyzing two-body Green's functions and complex dynamical effects.