Observing two-electron interactions with correlation-ARPES

TL;DR

This paper introduces correlation-ARPES, a novel experimental technique that directly measures two-electron interactions in quantum materials by analyzing correlations between photoemitted electrons, exemplified with phonon-mediated interactions.

Contribution

The paper presents correlation-ARPES, a new method enabling direct measurement of specific quasiparticle interactions, advancing the study of emergent phenomena in quantum materials.

Findings

Demonstrated correlation-ARPES can extract electron-electron interactions.

Showed the technique can identify phonon-mediated interactions.

Validated the method with charge density wave example.

Abstract

Identifying and studying the underlying two-electron interactions that give rise to emergent phenomena is a key step in developing a holistic understanding of quantum materials. This step is hindered by the lack of an experiment that can directly interrogate the interactions and the specific quasiparticles involved in the interaction simultaneously. We introduce correlation-ARPES (C-ARPES) as a new experimental method that overcomes this difficulty and directly measures the interactions between specific, chosen quasiparticles by measuring the correlations between two electrons photoemitted from the same pulse (but not the same photon). We illustrate how this technique can extract the underlying interactions, and demonstrate this with an example of phonon-mediated electron-electron interactions, such as those that give rise to charge density waves through the Kohn anomaly mechanism.