Our Vision.
We are new research group located on campus at the University of Arkansas , Fayetteville. Our vision is to search and build new nanoscale materials, structures and devices out of building blocks which Nature does not permit in the bulk. Our approach is based on the idea that by combining such antagonistic building blocks we may create materials and devices with novel and often very unusual properties properties and functionality.
Understanding physics of strongly correlated systems is the central challenge of modern condensed matter physics. Complex oxide systems are the most common class of materials found on Earth. Earliest examples known to humanity include Fe_2O_3 - ironstone and Fe_3O_4 - magnetite. Magnetite can be found in the brain cells of a tuna fish and is believed to be responsible for tuna's ability to navigate the ocean in a way which similar to the Giant Magneto-Resistance effect (GMR). On the other hand the same material is also known as a half-metallic system and is in the heart of a new field called spintronics. Recently another class of complex oxides called manganites (e.g. La_{2/3}Ca_{1/3}MnO_3) has generated a lot of attention. The manganites posses a rather peculiar feature called colossal magneto-resistance and show dramatic changes in resistivity with applied magnetic field. This feature alone made manganites a prime candidate for nano-magnetic switches. As a final example, one of the most exiting recent discovery in condensed matter physics is connected to another group of oxide compounds called - high-temperature super-conducting cuprates (e.g. La_{1-x}Sr_xCuO_4, YBa_2Cu_3O_7 or Bi_2Sr_2SaCu_2O_8).
From fundamental physics point of view, there exist an extremely interesting class of oxide materials known as Mott-Hubbard insulators. Typical examples of those include anti-ferromagnetic (AFM) oxides such as NiO, CoO, MnO etc. What makes Mott insulators so interesting is our striking inability to predict their electronic and magnetic from quantum theory. For example, despite enormous advances in theory we still cannot explain why NiO is an insulator and not a metal as predicted by the band theory. Among Mott insulators there exist another group of oxides (e.g. Va_2O_3 or Ti_2O_3) showing a metal-insulator (MI) transition which occurs below a certain characteristic temperature T_MI. Again the presence of the MI transition is one of the unexplained puzzles of modern physics. A common feature which unites the oxides with those rather "bizarre" properties is the presence of de-localized d-electrons of transition metals (e.g. Cu, Ni, Fe, Ru etc.) strongly coupled to oxygen p-orbitals. The enormous diversity and exceptional physical properties of complex oxides arise mostly from a delicate balance between de-localized electrons and effects of Coulomb interaction which tends to localize electrons.
Our group is actively involved in fabrication and advanced characterization of nano-structures built of complex oxides such as described above. The nano-scale adds an extra degree of complexity in to already extremely rich physics. In order to investigate complex oxide nano-structures we use synchrotron soft x-ray radiation (400 eV-3000 eV) and polarized neutron scattering. All experiments are performed at the world class facilities such as Advance Photon Source (Argonne National Lab, USA), the European Synchrotron Radiation Facility -ESRF (Grenoble, France) , ISIS (Rutherford Appleton Laboratory, UK) and Swiss Light Source - SLS, Switzerland. By using 3d generation soft X-ray radiation we are able to probe electronic structure of nanomaterial directly. Moreover by using left and right circularly popularized light and polarized neutron reflectivity we were able to investigate their electronic properties on nano-scale (down to a sub-monolayer!). For a recent example see our paper in Nature Physics, v.2 p.244 (2006)).
How do we do this
Oxide Laser MBE control multiplied by the power of large-scale research facilities and strong collaborations is the short answer.
