Condensed Matter Seminar- Applications and development of RIXS: study of cobaltates, nickelates and rhenates” with Dr. Alex Taekyung Lee
Physics Seminar
April 11, 2024
11:00 AM - 12:00 PM
Location
SES 2214
Calendar
Download iCal FileResonant Inelastic X-ray Scattering (RIXS) is an advanced technique that measures low-energy excitations such as phonons, magnons, and d-orbital splitting. While X-ray Absorption Spectra (XAS) is widely used to study the electronic and spin states of materials, it has limitations due to the broadening of peaks caused by the core-hole lifetime. RIXS overcomes this challenge through 2D spectroscopy mapping as a function of incident energy and energy loss, enabling high-resolution measurement of energy excitations. This talk will explore several applications of RIXS for materials: Sr2CrReO6, LaNiO3, LaCoO3, CoO, and LaCoO3+LaTiO3 (LCO/LTO) superlattices.
We have measured the RIXS of Sr2CrReO6, observing a strong low-energy peak near 0.2 eV, attributed to the spin-flip process of Re. Additionally, we identified two nondegenerate magnon bands, influenced by either Re or Cr spins, with the Re band being lower in energy. Our recent synthesis of LaCoO3+LaTiO3 superlattices revealed strong orbital polarization of Co, with DFT+U predictions indicating a 2+ charge state and a high-spin configuration for Co. By comparing the RIXS spectra of Co in LCO, CoO, and LCO/LTO superlattices, we study the charge and spin states of the Co ion.
Finally, we combine a DFT+U based theoretical approach and RIXS. Since the DFT+U calculations can capture the physics of both the dispersive and localized bands, this approach is capable of describing the broad, fluorescent-like features in RIXS as well as localized excitations. We find that this theoretical approach allows us to interpret the RIXS spectra for Co- and Ni-based bulk materials and superlattices.
References
[1] G. Marcard, A. T. Lee et al., Phys. Rev. B 108, 075132 (2023)
[2] S. J. Lee, A. T. Lee et al., Phys. Rev. Lett. 123, 117201 (2019), A. T. Lee and S. Ismail-Beigi, Phys. Rev. B 101, 144423 (2020), A. T. Lee, H. Park, and S. Ismail-Beigi, Phys. Rev. B 103, 125105 (2021)
Date posted
Apr 11, 2024
Date updated
Apr 11, 2024