Understanding and Controlling Conductivity Transitions in Correlated Solids: Spectroscopic Studies of Electronic Structure in Vanadates (Final Report)
- Boston Univ., MA (United States). Dept. of Physics
This research project is focused on synchrotron radiation based x-ray spectroscopic studies of the metal to insulator transition in vanadium oxides. In doing so, we developed a fundamental understanding of the origins of conductivity transitions in correlated electron materials. Conductivity transitions can be driven by external and internal mechanisms, including electric and magnetic fields, chemical doping, defects, disorder, pressure, dimensionality, and temperature. Vanadium oxides, and vanadium dioxide in particular, display particularly complex electronic phenomena. Binary vanadium oxides, and ternary oxides with substituted metal cations, exhibit a broad range of complex conductivity transitions, as well as charge ordering transitions, structural phase transitions, frustrated spin structures, superconductivity, and unusual magnetic properties. As such, vanadates are a prototypical class of correlated material, where fundamentally important physical themes can be explored, both experimentally and theoretically. The experimental tools used were soft x-ray emission spectroscopy (XES), soft x-ray absorption spectroscopy (XAS), resonant inelastic soft x ray scattering (RIXS), x-ray photoemission spectroscopy (XPS), angle resolved photoemission spectroscopy (ARPES), and spectroscopic photoemission low energy electron microscopy (SPELEEM). This broad range of techniques delivered data that was used to understand the electronic structure in these oxides. Vanadium oxides as single crystals, thin films, polycrystalline powders, and nanoparticles were studied to determine the influence of the physical structure the materials properties. A rich and varied selection of experiments were performed, and by combining the information gathered by our x-ray spectroscopic techniques, we developed a comprehensive understanding of electronic structure in vanadium oxides. We measured band structures and Fermi surfaces, studied the coupling between collective excitations and quasi-particles, measured the local, site and element specific electronic structure, as well as the cation charge state, measured orbital hybridization, and measured element specific low energy valence excitations such as dd* and charge transfer excitations.
- Research Organization:
- Boston Univ., MA (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Materials Sciences & Engineering Division
- DOE Contract Number:
- FG02-98ER45680
- OSTI ID:
- 1498734
- Report Number(s):
- DOE-BU-45680
- Country of Publication:
- United States
- Language:
- English
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