University of California, Berkeley
Periodically Modulated Electronic Wavefunctions in Transition Metal Oxides Explored by Resonant X-ray Scattering
Familiar x-ray diffraction experiments produce a Fourier transform of the atomic landscape via elastic scattering and are routinely used to study the structure of solids. Resolving the inelastic energy exchange between photons and atomic ions probes the dynamical structure factor, a quantity that reveals collective dynamics of the atomic lattice and their dispersion. These techniques provide unambiguous windows into atomic order in solids. What if the principle could be used analogously to probe electronic order in correlated “quantum materials”?
By tuning the x-ray energy to electronic transitions and judiciously exciting electrons into states near the Fermi level, spatial modulations and temporal dynamics of electronic wavefunctions can be studied in Fourier space. Propelled by technological advances in synchrotron science over the last decades, Resonant (in)elastic X-Ray Scattering (RXS) provides this exciting and powerful tool to investigate the electronic structure of solids. Quintessential cases are transition metal oxides, where strong electronic correlations yield nontrivial, ordered patterns of the spin, charge and orbital character of the d-wavefunctions.
In this talk, let us discuss examples of how these subtle phases can be detected using RXS and how they can be tuned by external conditions like strain, interfacial geometries, and applied magnetic fields. These include the discovery and stabilization of charge density wave order in superconducting cuprates, dimensionality-induced magnetism in perovskite nickelates, and ‘Kitaev frustration’ exposed by external magnetic fields in the honeycomb iridate Li2IrO3. Finally, I will discuss the future of RXS with new light sources such as the nearby NSLS-II.