SFB 1238 | November 26, 14:30
Direct visualization of lattice and electronic structures in quantum materials by advanced microscopy and spectroscopy
The rich properties of strongly correlated and quantum materials derive from complex interplay between atomic lattice, charge, spin, and orbital interactions. Direct experimental measurements of these order parameters in real space are therefore important tools for understanding many emergent phenomena including charge order, superconductivity, and magnetism, especially in systems with heterogeneity or phase coexistence/competition. Locally, electron energy loss spectroscopy (EELS) in the scanning transmission electron microscope (STEM) is a powerful platform to probe the elemental and electronic configuration of new materials with spatial resolution down to the atomic scale for quantifying valence states and charge evolution, especially in atomically-designed heterostructures or across buried interfaces [1,2,3]. Alternatively, harnessing beyond-dipole spectroscopy via s-orbital nonresonant inelastic x-ray scattering (sNIXS) enables direct, real-space mapping of orbital configurations without input from atomistic or first-principles modeling [4]. Here, I will highlight these advanced spectroscopic methods through their application across the families of strongly correlated nickel oxide compounds which exhibit rich physical properties ranging from superconductivity to metal-insulator transitions. Local EELS measurements in infinite-layer nickelate superconductors demonstrate key distinctions from the seemingly analogous high-Tc cuprates and reveal the importance of the film-substrate interface on their macroscopic properties. We use sNIXS to directly measure spin configurations and effective crystal field splitting more broadly across formal valences from 1+ to 3+ [5], demonstrating the potential of this technique for more exotic compounds in the future [6].
1. Goodge et al. PNAS 118(2), e2007683118 (2021).
2. Goodge et al. Nat. Mater. 22, 466–473 (2023).
3. Husremovic et al. Nat. Comm. 16, 1208 (2025).
4. Yavaș et al. Nat. Phys. 15, 559-562 (2019).
5. Abarca Morales et al. in preparation.
6. Ko et al. Nature 638, 935–940 (2025); Bhatt et al. arXiv:2501.08204 (2025).
Max Planck Institue for Chemical Physics of Solids, Dresden
PH2
Contact: Markus Grüninger / Matteo Cacco