Photoemission tomography of excitons in 2D systems: momentum-space signatures of correlated electron-hole wave functions

TL;DR

This paper develops a computational method to simulate and interpret the momentum-space signatures of excitons in 2D materials using photoemission spectroscopy, incorporating many-body effects and light-matter interactions.

Contribution

It introduces exciton photoemission orbital tomography (exPOT) for periodic systems, linking GW+BSE theory to experimental observables and including matrix element effects.

Findings

Demonstrates exciton photoemission in hexagonal boron nitride

Shows dependence of photoemission angular distribution on probe polarization

Extends framework to momentum-dark excitons

Abstract

The momentum-space signatures of excitons can be experimentally accessed through time-resolved (pump-probe) photoelectron spectroscopy. In this work, we develop a computational framework for exciton photoemission orbital tomography (exPOT) in periodic systems, enabling the simulation and interpretation of experimental observables within many-body perturbation theory. By connecting the GW +Bethe-Salpeter equation (BSE) approach to photoemission tomography, our formalism captures exciton photoemission in periodic systems, explicitly incorporating photoemission matrix element effects induced by the light-matter interaction via the probe pulse. The correlated nature of electrons and holes introduces distinct consequences for excitonic photoemission. Using the prototypical two-dimensional material hexagonal boron nitride, we demonstrate these effects, including a dependence of the photoemission angular distribution on the pump pulse polarization. Moreover, our framework extends to excitons with finite center-of-mass momentum, making it well-suited to studying momentum-dark excitons. This provides valuable insights into the microscopic nature of excitonic phenomena in quantum materials.