Development of ultra-high efficiency soft x-ray angle-resolved photoemission spectroscopy equipped with deep prior-based denoising method

Soft x-ray angle-resolved photoemission spectroscopy (SX-ARPES) is one of the most powerful spectroscopic techniques to visualize the three-dimensional bulk electronic structure in reciprocal lattice space. Compared with ARPES employing low-energy photon sources, the time burden imposed by a lower photoelectron yield, stemming from the photoionization cross-section, has been a persistent technical challenge. To address this challenge, we have developed a noise-reduction system by using the deep prior-based approach and integrated it into the micro-focused SX-ARPES (μSX-ARPES) system at BL25SU in SPring-8. The implemented system effectively eliminates instrumental artifacts, such as grid and spike structures typical of ARPES data acquired using the voltage Fixed mode, within ∼30 s. We demonstrate, through the μSX-ARPES measurements on a single crystal of CeRu2Si2, that data with sufficient statistical accuracy can be obtained in ∼40 s. In addition, we present the potential of high signal-to-noise ratio ARPES measurement, achieving an energy resolution of 51.6 meV at an excitation energy of 708 eV in μSX-ARPES measurements on polycrystalline gold. Our developed system successfully reduces the time burden in SX-ARPES and paves the way for advancements in lower photoelectron yield measurements, such as those requiring higher energy resolution and three-dimensional nonequilibrium measurements.