Image resonance in the many-body density of states at a metal surface

TL;DR

This paper investigates the electronic density of states at a metal surface, revealing a broad unoccupied surface resonance linked to image states, influenced by many-body correlation effects.

Contribution

It introduces a formalism that captures the continuous spectrum of a semi-infinite metal surface and identifies a broad surface resonance due to many-body effects.

Findings

Presence of an unoccupied surface resonance at the image state position

Resonance covers the entire Rydberg series of image states

Many-body correlations shift spectral weight, creating the resonance

Abstract

The electronic properties of a semi-infinite metal surface without a bulk gap are studied by a formalism able to account for the continuous spectrum of the system. The density of states at the surface is calculated within the $GW$ approximation of many-body perturbation theory. We demonstrate the presence of an unoccupied surface resonance peaked at the position of the first image state. The resonance encompasses the whole Rydberg series of image states and cannot be resolved into individual peaks. Its origin is the shift in spectral weight when many-body correlation effects are taken into account.