Interband interaction between Ge states and surface resonance band of Pb on Ge(001)

TL;DR

This study uses angle-resolved photoelectron spectroscopy to reveal how Pb adsorption on Ge(001) induces a surface resonance band that interacts with and modifies the bulk-like Ge valence bands, demonstrating hybridization effects.

Contribution

It uncovers the existence of a surface resonance band in Pb/Ge(001) and shows its interaction with Ge valence bands, a novel insight into surface-bulk state coupling.

Findings

Identification of a persistent surface resonance band in Pb/Ge(001)

Reduction of G3 band effective mass due to surface resonance interaction

Hybridization between Ge states and surface resonance states observed

Abstract

We investigate the valence band structure of Pb on Ge(001) by Angle-Resolved Photoelectron Spectroscopy. Three Ge bands, G1, G2, and G3, were observed on Ge(001) 2x1 clean surface. In addition to these three bands, a forth band (R band) is found in the 2 ML of Pb coverage. The R band continues to appear even when the surface superstructure changed. The position of the R band does not depend on Pb coverage. These results indicate that the R band derives from Ge subsurface states known as surface resonance states. Furthermore, the effective mass of G3 is significantly reduced when this forth band exists. We found that this reduction of the G3 effective mass was explained by the interaction of the G3 and the surface resonance band. Consequently, the surface resonance band penetrates the Ge subsurface region affecting the Ge bulk states. We observed the hybridization between Ge states and the surface resonance states induced by Pb adsorption.