Photoemission response of 2D states

TL;DR

This paper presents a Fourier analysis-based framework that links the photoemission response of 2D electron states to their wavefunctions, enabling the characterization of various surface and interface states through ARPES data.

Contribution

It introduces a novel formalism connecting ARPES intensity patterns to wavefunction Fourier components, facilitating fundamental property access of 2D states.

Findings

Periodic ARPES peaks relate to wavefunction Fourier series.

Aperiodic hv-dependence indicates localized states.

Method applied to multiple experimental data sets.

Abstract

A lucid Fourier analysis based description of the photoemission process is presented that directly relates photon energy (hv) dependent ARPES response of two-dimensional (2D) electron states to their wavefunctions. The states formed by quantum confinement of bulk Bloch waves (including Shockley-Tamm type surface and interface states, and quantum-well states) show periodic peaks of ARPES intensity as a function of hv. Amplitudes of these peaks reflect Fourier series of the oscillating Bloch-wave component of the wavefunction, and their broadening spatial confinement of its envelope function. In contrast, the 2D formed by local orbitals (dangling bonds and defects at the surface or interface) show aperiodic hv-dependence, where the rate of decay reflects localization of these states in the out-of-plane direction. This formalism sets up a straightforward methodology to access fundamental properties of different 2D states, as illustrated by analysis of previous photoemission experimental data including the paradigm Al(100) surface state, quantum-well states in multilayer graphene and at the buried GaAlN/GaN interface, and molecular orbitals.