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Dr. Chun Ning Lau - General Colloquium
March 4, 2004
Dr. Chun Ning Lau
Hewlett-Packard Laboratories
Title: Nanoscale superconductivity and Electronics
It has proven to be fascinating and rewarding to investigate and exploit properties of nanoscale systems, such as carbon nanotubes, nanowires and molecules. The first part of my talk will focus superconductivity in ultrathin nanowires. We demonstrated that superconductivity is suppressed by the macroscopic quantum tunneling of the phase of the superconducting order parameter, and the residual resistance depends exponentially on the wire diameter. This work helps to establish a limit to the miniaturization of superconducting electronics, and may have important implications for quantum computing based on superconductors.
The second part of my talk focuses on electrical transport in molecular devices. In particular, conductance switching in metal/molecule/metal structures has received much attention because of their potential use as nano-scale memory elements. However, the switching mechanism remains controversial. By using a novel scanned-probe technique to image Pt/stearic acid monolayer/Ti junctions, we were able to locate individual nanometer-scale switching centers that appeared and disappeared when the device was switched to high and low conductance states respectively. Our results strongly suggested that individual nanoscale filaments through the molecular layer give rise to conductance switching in our molecular structures, and enable better understanding and design of molecular devices.