Quantum solids and devices under a dark-field x-ray microscope at modern light sources
Abstract: Recent brightness upgrade of synchrotron-radiation facilities worldwide is ushering in novel opportunities virtually in all fields of materials research especially imaging using x-rays. This talk focuses on advances made at the Advanced Photon Source in a lens-based diffraction-contrast imaging modality called dark field x-ray microscopy (DFXM) [1-7] and its prospects leveraging brightness upgrade at future sources (e.g., APS-U). In DFXM a Bragg diffracted beam from an ordered material is used to form a two-dimensional full-field real-space image of ‘mesoscale’ features (e.g. charge-ordered domains, twins, and dislocation network) by passing it through an x-ray objective lens. Mesoscale information is encoded on a crystal Bragg peak, a super-lattice (e.g., due to charge, magnetic, or orbital order) peak, or an epitaxial-film peak in the form of spatial variation of intensity. These intensity variations, or contrasts, reveal an incisive real-space picture with a field-of-view of tens of nanometers to well beyond tens of micrometers [4,5]. Illustrative examples sampled from recent work including charge-density waves [8], long-range modulations below a ‘nematic’ transition [9], switching behavior neuromorphic devices [4,10], and role of local actors across a magneto-structural phase transition [2], are presented. Furthermore, an emerging novel approach using structured illumination [9] to reconstruct mesoscale structures in three dimensions is outlined. Finally, new directions in DFXM to leverage increased coherence are discussed.
Bio: Zahir Islam is a Physicist at Argonne National Laboratory. He focuses on developing new instrumentation, techniques, and methodology for advancing quantum-materials research at the Advanced Photon Source. These include a dedicated 5 Tesla superconducting magnet and 30 Tesla pulsed magnet for single-crystal diffraction studies in magnetic field. Currently, he is fully developing Dark Field X-ray Microscopy (DFXM). He received his B.S. degree in Physics from Bemidji State University in Minnesota. In 1999, he completed his Ph.D. in Experimental Condensed Matter Physics at Iowa State University. His thesis comprised of computational and experimental investigations of the role of electronic band tuning of Fermi-surface topology and single-ion anisotropy in long-range magnetic order in a family of rare-earth compounds. He is an active member of American Physical Society Group on Instrument and Measurement Science executive committee.
