Multimodal tool combining multichannel HREELS and ARPES/XPS to study electron-phonon coupling

Electrons and phonons couple in a material and influence each other's behaviors. The "kinks" in electronic band dispersion observed by angle-resolved photoemission spectroscopy (ARPES) are explained by electron-phonon coupling, while gapless electron states produce kinks in the phonon dispersion, known as Kohn anomalies. This highlights the need for multimodal characterization tools to investigate phonon dispersion and electronic band dispersion. High-resolution electron energy loss spectroscopy (HREELS) is a surface sensitive technique capable of obtaining vibrational signatures of surface phonons, plasmons, and adsorbates. Multimodal characterization has been difficult using traditional single channel HREELS because it requires its own detector, the measurements are time consuming, and angular resolution is limited. To improve the efficiency of HREELS measurements and to realize multimodal measurement with photoemission spectroscopy, we developed a solution by combining a monochromatic collimated electron source and a hemispherical electron analyser, commonly used for ARPES/XPS. The 2D detector of the analyser simultaneously measures hundreds of channels in both the energy and angular directions, and the measurements are orders of magnitude faster than the single channel setups. This setup allows multimodal characterization combining state-of-art HREELS and ARPES/XPS using the same analyser to study the interplay between electronic properties and phonon dynamics.