A highly sensitive TES spectrometer for resonant elastic/inelastic X-ray scattering study of quantum materials

Resonant inelastic X-ray scattering (RIXS) as well as resonant elastic X-ray scattering (REXS) have been appreciated as compelling techniques in research of quantum materials. It is because the techniques deliver element-, site-, and valence-specific information through a resonance-enhanced photon-in/photon-out process. Conventionally, grating-based spectrometers have been used to measure the scattered photons in RIXS/REXS in the soft X-ray regime. However, we often experience a lack of sensitivity when a weak signal needs to be detected. Here, we introduce a novel method to overcome such difficulty using transition-edge sensors (TESs). A spectrometer built upon an array of TESs has detection efficiency that is orders of magnitude larger than a conventional grating spectrometer and has shown a spectral coverage broader than 1 keV and a moderate energy resolution of 1.5 eV (FWHM) at 500 eV. A TES spectrometer was recently integrated with the soft X-ray scattering setup at beamline 13-3 of the Stanford Synchrotron Radiation Lightsource (SSRL) and was successfully commissioned. In this poster, we will present new results taken with this new RIXS/REXS + TES approach. We believe that this approach can bring impacts to a wide range of quantum materials studies.