High-energy photoemission final states beyond the free-electron approximation

Area of Science:

• Solid-state physics
• Materials science
• Surface science

Background:

• Three-dimensional (3D) electronic band structure is key to understanding phenomena like topological phases and phase transitions.
• Current analysis of Angle-Resolved Photoemission Spectroscopy (ARPES) data often relies on simplified free-electron approximations for photoemission final states.

Purpose of the Study:

• To investigate the complexity of photoemission final states in soft-X-ray ARPES.
• To challenge the common free-electron approximation in 3D band structure determination.
• To analyze the origins of spectral peak broadening and complex structures observed in ARPES data.

Main Methods:

• Soft-X-ray ARPES experiments on silver (Ag) metal.
• Analysis of spectral peak structures and broadening.
• Investigation of multiband final states incorporating multiple Bloch waves.
• Cross-material analysis including Silicon (Si) and Gallium Nitride (GaN).

Main Results:

• Soft-X-ray ARPES data from Ag metal demonstrates that final states are more complex than previously assumed, even at high energies.
• These complex final states involve multiple Bloch waves with varying out-of-plane momenta.
• This complexity leads to intricate spectral peak structures and broadening in the observed 3D electron states.

Conclusions:

• The free-electron approximation is insufficient for accurate 3D band structure determination using ARPES, especially at higher excitation energies.
• The identified multiband final states significantly impact spectral features and require consideration for precise band structure mapping.
• These findings are essential for advancing ARPES methodologies for accurate 3D band structure analysis in diverse materials.