Competing periodicities in a single atom wire

1. Electrical Transport in Thin Film NanostructuresHanno H. Weitering, The University of Tennessee, DMR 0244570 The smallest wire width in mass produced electronic devices is about 50 nm, or about 500 atoms across. The ultimate limit of thinness would be wires of only one atom wide. Such wires can be made now, although not for any working electronic device, and it is important to know their properties for future technology. Atom wires can be created via self-assembly on vicinal silicon surfaces. We addressed their formation, stability, metallicity, and the role of disorder. Gallium atom wires show entropic disorder that limits their structural perfection. On the other hand, Au-induced atom wires reveal three competing charge density wave instabilities (or a multiband Peierls instability). Phase slips in these density waves represent fractionally charged quasi-particles that can be imaged and spatially manipulated with the tip of a scanning tunneling microscope. Competing periodicities in a single atom wire Fractional quantum numbers in a phase slip Phys. Rev. Lett.96, 076801 (2006) and AIP Physics News Update # 767

2. Electrical Transport in Thin Film NanostructuresHanno H. Weitering, The University of Tennessee, DMR 0244570 Education: Two graduate students (Murat Özer and Eun Ju Moon) and one postdoc (Jiandong Guo) were supported by this award. Murat Özer was first author on a paper in the March 2006 issue of Nature Physics showing that films only a few atom layers thick can carry enormous supercurrents—defying theories that superconductivity is typically weak at the nanoscale. For this work, he won the prestigious Nottingham Prize for best student presentation at the 2006 Physical Electronics Conference at Princeton University. He also received the University Chancellor’s Citation for Professional Promise and a Paul H. Stelson Research Fellowship from the Physics Department. Murat Özer received his Ph.D. degree at UT in the summer of 2006. He is currently postdoc at the University of Texas in Austin. Dr. Jiandong Guo pioneered optical studies of thin film nanostructures. He left the group in October 2005 to become a junior physics professor at the Chinese Academy of Sciences in Beijing. Eun Ju Moon began her thesis research in January 2005. She has build dedicated measurement equipment for in-situ studies of quantum transport in thin film nanostructures and is continuing her Ph.D. dissertation research. Societal Impact: Nanoscience represents a very promising avenue for future innovations in e.g. the physical sciences, medicine, and information technology. A key requirement for making functional nanodevices is the ability to acquire perfect control of their structure and morphology. A viable way to accomplish this is to exploit quantum mechanical laws while tuning and assembling nano structures. This work represents an important case-study, showing: (1) how quantum mechanics can be used to control the structure and morphology of thin film nanostructures at the atomic level, and (2) how the “quantum engineered morphology” of thin films relates to one of their most appealing functionalities, namely dissipation-free electrical conductivity or “superconductivity.”