Confined monolayer Ag as a large gap 2D semiconductor and its momentum resolved excited states

TL;DR

This study reveals that monolayer silver confined between bilayer graphene and SiC acts as a large-gap 2D semiconductor with unique excited state properties, confirmed by ARPES and theoretical calculations.

Contribution

It demonstrates that monolayer Ag is a large-gap 2D semiconductor with momentum-resolved electronic states, combining experimental ARPES data with GW-corrected DFT calculations.

Findings

Monolayer Ag has a band gap greater than 1 eV.

Valence band dispersion matches GW-corrected DFT predictions.

Conduction band shows an anomalously large effective mass of 2.4 m0.

Abstract

2D materials have intriguing quantum phenomena that are distinctively different from their bulk counterparts. Recently, epitaxially synthesized wafer-scale 2D metals, composed of elemental atoms, are attracting attention not only for their potential applications but also for exotic quantum effects such as superconductivity. By mapping momentum-resolved electronic states using time-resolved and angle-resolved photoemission spectroscopy (ARPES), we reveal that monolayer Ag confined between bilayer graphene and SiC is a large gap (> 1 eV) 2D semiconductor, consistent with GW-corrected density functional theory. The measured valence band dispersion matches the DFT-GW quasiparticle band. However, the conduction band dispersion shows an anomalously large effective mass of 2.4 m0. Possible mechanisms for this large enhancement in the apparent mass are discussed.