Ultra-High-Resolution Resonant Inelastic X-ray Scattering at TPS 41A: A New Window into Quantum Materials

Hsiao-Yu Huang^1*

¹Scientific Research Division, National Synchrotron Radiation Research Center, Hsinchu, Taiwan

* Presenter:Hsiao-Yu Huang, email:huang.hy@nsrrc.org.tw

Resonant inelastic X-ray scattering (RIXS) has emerged as one of the most versatile spectroscopies for studying quantum materials at modern synchrotron facilities. By combining elemental and orbital selectivity with momentum resolution and polarization control, RIXS provides direct access to elementary excitations involving spin, orbital, charge, and lattice degrees of freedom.

At the TPS 41A soft X-ray RIXS beamline, we have developed an active-grating monochromator and spectrometer (AGM–AGS) system that achieves a world-leading resolving power of 42,000 at the O K-edge. This capability enables quantitative studies of low-energy excitations such as charge-density-wave fluctuations, lattice dynamics, and spin excitations in correlated and topological materials.

This talk will introduce the fundamental principles and instrumentation of RIXS and highlight recent scientific examples. These results illustrate how RIXS complements existing synchrotron tools and opens new frontiers for exploring quantum materials.

References:
M. Mitrano, S. Johnston, Y.-J. Kim, and M. P. M. Dean. Exploring quantum materials with resonant inelastic X-Ray scattering. Phys. Rev. X 14, 040501 (2024).
A. Singh, H.-Y. Huang, Y. Y. Chu et al., Development of the soft X-ray AGM–AGS RIXS beamline at the Taiwan Photon Source. J. Synchrotron Radiat. 28, 977 (2021).
H.-Y. Huang, A. Singh, C. Y. Mou et al., Quantum fluctuations of charge order induce phonon softening in a superconducting cuprate. Phys. Rev. X 11, 041038 (2021).
A. Singh, H.-Y. Huang, J. D. Xie et al., Unconventional exciton evolution from the pseudogap to superconducting phases in cuprates. Nat Commun 13, 7906 (2022).
Q. Li, H.-Y. Huang, T. Ren et al., Prevailing charge order in overdoped La 2-x Sr x CuO 4 beyond the Superconducting Dome. Phys. Rev. Lett. 131, 116002 (2023).
D. Jost , H.-Y. Huang, M. Rossi et al., Low temperature dynamic polaron liquid in a manganite exhibiting colossal magnetoresistance. Phys. Rev. Lett. 132, 186502 (2024).
Z. Wang, Y. Guo, H.-Y. Huang et al., Spin excitations and flat electronic bands in a Cr-based kagome superconductor. Nat Commun 16, 7573 (2025).

Keywords: RIXS, quantum materials, elementary excitations, soft X-ray spectroscopy