Superconductor Materials Topics at Texas Materials Institute
The discovery of high temperature superconductivity with copper oxide compounds in 1986 resulted in a large amount of scientific research worldwide. During the years since the initial discovery, University of Texas scientists have played a central role in the development of the existing science base in this area. Associated with the TMI are a number of the world’s leaders in the area of superconductor research. The processing of reliable, reproducible, and durable superconductor devices and conductors in a cost-effective manner from complicated oxide superconductors represents an essential and difficult problem for materials researchers. Some of the TMI efforts in the area of superconductor research are highlighted below.
Development of a reliable materials base
The poor material properties associated with these brittle and reactive ceramic compounds have encouraged scientists to continue to search for alternative superconductor materials as well as to find chemically benign processing methods. Careful studies of the structure/reactivity characteristics of cuprate compounds have been completed recently by TMI scientists. Studies focusing on the mechanism of decomposition of high-Tc samples have revealed strong coupling between water reactivity, copper redox chemistry and oxide/oxygen evolution/uptake. This new mechanistic knowledge has led TMI faculty to the development of a new materials base that is suitable for the preparation of devices and conductors that exhibit enhanced performance characteristics.
Single crystal materials
In the recent past, members of the TMI have developed a number of strategies for the growth of high quality single crystal samples of the oxide superconductors. Here Y-Ba-Cu-O and related materials have been prepared and characterized using a number of magnetic, transport, diffraction, and scanning probe methods. Members of the TMI are now in the process of developing techniques for growing single crystals of the stabilized high-Tc formulations discussed above. Moreover, a new NSF-funded UT traveling-solvent floating- zone system (image furnace) is available to TMI researchers for the growth of very large crystals.
Tunneling spectroscopy provides unsurpassed sensitivity and resolution in probing the superconducting quasi-particle density of states, yielding information about the superconducting mechanism and order parameter. TMI scientists have completed a number of important tunneling studies to assess the normal state and superconducting electronic states at the exterior regions of thin film and single crystal samples. Moreover, sensitive STM and MFM methods operable over a wide temperature range have been completed to evaluate the local structure and defect densities that exist at the surfaces of the oxide compounds.