Pushing the space-charge limit in electron momentum microscopy

Abstract:

Angle-resolved photoelectron spectroscopy (ARPES) is a key technique for studying the momentum-dependent electronic structure of materials, particularly in the context of novel materials like high-temperature superconductors and topological insulators. Recent advancements, such as time-of-flight (ToF) momentum microscopy, have significantly enhanced the resolution and spatial confinement of ARPES measurements. However, space-charge effects—caused by the emission of large numbers of photoelectrons during measurements—pose a major challenge by distorting spectral data, especially near the Fermi edge.

This perspective discusses the work of Schönhense et al., which introduces a correction algorithm to mitigate space-charge-induced distortions in ToF momentum microscopes. The algorithm, based on ray-tracing simulations and mean-field models, compensates for interactions between emitted photoelectrons, restoring the energy distribution near the Fermi edge. The study demonstrates that, despite space-charge effects leading to energy shifts and increased background intensity, the Fermi edge remains sharp, making it possible to recover fine details of the Fermi surface.

The article emphasizes the potential of this correction method to increase data acquisition efficiency by allowing higher photon pulse intensities without sacrificing accuracy. Additionally, it highlights the importance of automated data processing in handling the large volumes of data generated by modern ARPES systems. These advancements enable more precise 3D band structure tomography, time-resolved experiments, and the exploration of complex materials, pushing the limits of electron momentum microscopy and broadening its applications in condensed-matter physics.