Low Temperature Scanning Tunneling Microscopy

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w:\awards\awards96\*.doc 9623448 DeLozanne This condensed matter physics project will continue development of a low-temperature, ultra-high-vacuum, scanning tunneling microscope (STM). The STM is used for in-situ cleavage of high-Tc materials. Preliminary STM study of the clean surfaces has revealed novel structural features and an reproducible gap in YBCO materials. The origin of the structural features is uncertain and will be further investigated in this project. The instrument capabilities will be improved to allow a lower base operating temperature, and lower noise. This will expand the range superconducting materials that can be investigated. Of particular interest are measurement of vortex structure and charge density waves in superconductors. This is a fundamental project. The results will be of significance for theories of superconductivity, and may lead to development of new superconducting materials. %%% This project will continue development of a surface structure determination tool, a scanning tunneling microscope (STM), which has unique capabilities. With this instrument it is possible to take a small single crystal of a high-Tc superconductor, cool it to very low temperatures (20 K), cleave the crystal, and study the surface structure with the STM at the low temperature. Preliminary data have revealed unusual structural features in high-Tc materials whose origin is uncertain, but which certainly relevant to mechanisms of high-Tc superconductivity. This project will clarify the nature of the structural properties of several high-Tc materials, and will study the temperature dependence of the phenomena. The instrument will be further developed to allow a lower base temperature, which will increase the range of superconducting materials that can be investigated. This is a fundamental project in condensed matter physics. The results will be of significance for theories of superconductivity, and may lead to development of new superconducting materials. ***