Ultraviolet photon source advances time-resolved angle-resolved photoemission spectroscopy

Time-resolved angle-resolved photoemission spectroscopy (ARPES) is a prime experimental technique for unraveling details around the electronic structure of crystalline solids. The method can directly probe the single-particle spectral function, which contains information related to band dispersion and many-body interactions. ARPES is an indispensable tool for understanding emergent phenomena in quantum materials, where quasiparticles or collective excitations are core ingredients and naturally invoke a description beyond the simple noninteracting single particle picture.

The advent of femtosecond high-power lasers and advancements in synchrotron-based light sources and electron analyzers over the past few decades have enhanced the technique’s capacities by orders of magnitude. The technique continues to rapidly evolve in the direction of increased repetition rate, photon flux, improved time and energy resolutions, photon energy and momentum range coverage, and pump versatility.

Toward these ends, Guo et al. introduced a novel ultraviolet light source designed to achieve high energy resolution at high repetition rates in the ARPES setup. They aimed to resolve detailed electronic structure features in quantum materials, such as superconducting gaps in superconductors.

“We have achieved a setup for time-resolved ARPES with unprecedented energy resolution (for a high harmonic generation system) with high repetition rate and a tunable pump,” said co-author Oscar Tjernberg. “Together this opens up possibilities for time-resolved studies of dynamics and phase transitions where the relevant energy/momentum scales are small. Typical examples are superconductors, transition metal dichalcogenides, topological insulators and Weyl semimetals.”

The combination of high repetition rate, wide range of photon energies, and continuously tunable wide range of pump energies with a time-of-flight detector enables the study of ultrafast dynamics in most crystalline materials.

Source: “A narrow bandwidth extreme ultra-violet light source for time- and angle-resolved photoemission spectroscopy,” by Qinda Guo, Maciej Dendzik, Antonija Grubišic-Cabo, Magnus H. Berntsen, Cong Li, Wanyu Chen, Bharti Matta, Ulrich Starke, Bjorn Hessmo, Jonas Weissenrieder, and Oscar Tjernberg, Structural Dynamics (2022). The article can be accessed at https://doi.org/10.1063/4.0000149 .