[PAST EVENT] Physics Colloquium - Mumtaz Qazilbash
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- Open to the public
Mumtaz Qazilbash, William & Mary Physics, Title of Talk: Recent insights into the metal-insulator transition of vanadium dioxide (VO2)
Metal-insulator transitions are among the most fascinating and least understood phenomena in condensed matter physics. Metal-insulator transitions lead to significant changes in the electronic conductivity and optical properties, and are generally accompanied by structural and magnetic transformations due to a complex interplay between charge, spin, orbital, and lattice degrees of freedom. The thermally-driven metal-insulator transition (MIT) in bulk vanadium dioxide (VO2) is accompanied by a structural distortion that leads to pairing of all the vanadium atoms in the insulating phase. This V-V pairing has long been thought critical to the emergence of insulating behavior. We shall present our latest experiments on ultrathin VO2 films grown on TiO2 substrates. We demonstrate that the MIT in ultrathin VO2 films occurs without the V-V structural distortion. Our results establish a route to a purely electronic MIT that is driven by electron-electron interactions. We shall also present our recent experiments and results on infrared nano-imaging and nano-spectroscopy of VO2 films. The development of table-top, broadband infrared light sources in my lab has enabled nano-spectroscopy experiments on VO2 and other materials.