This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).
This collaborative project will investigate the physics of electronic mesoscopic structures. These structures are made of a large number of atoms, but are sufficiently small to exhibit quantum phenomena that are not found in macroscopic objects. Understanding how the smaller size affects electronic properties is an intriguing problem from the standpoint of basic physics, as well as an essential step towards progress for faster and smaller electronics, that can even possibly exploit such quantum phenomena. The specific structures being investigated are made with carbon nanotubes, consisting of a layer of carbon atoms wrapped in the shape of a cylinder, with a diameter approximately 100,000 times smaller than the diameter of a human hair. Due to quantum mechanics, charges propagating along the nanotube behave like waves, whereas multiple electrodes connected to the tube behave like rocks in a shallow and narrow pond, obstructing wave propagation and causing reflections and ripples. This project will study how these phenomena affect electrical properties. It will also study whether novel states of matter could arise when the sample size is reduced to such small dimensions. More specifically, it will investigate whether and under which conditions carbon nanotubes may be novel superconducting materials. If successful, this study will provide much needed insight on new mechanisms for superconductivity and how to control superconducting properties, possibly paving the way towards the discovery of superconductors that work at temperatures close to room temperatures. The educational impact of this program goes well beyond the direct support of the postdoctoral fellow and the graduate student working on the project. Connections with this research are continuously developed in courses for non-science majors and physics majors, by introducing lectures on nanotechnology and high-resolution microscopy.
Carbon nanotubes are ideal mesoscopic objects to study properties of low-dimensional, phase coherent transport, because structures smaller than the phase coherence length (on the order of 1 micrometer) can be easily realized. This project will focus on a combined experimental and theoretical investigation of three manifestations of coherent transport:1) Nanotubes have been shown to act as coherent electron waveguides. This project will probe how multiple electrodes on a single nanotube create multiple standing waves in the nanotube and affect transport properties, including non-local effects, where transport in one nanotube section is affected by the adjacent sections; 2) Nanotubes connected to superconducting electrodes through a normal metal layer are the smallest point contacts and they can detect coherent transport due to the superconducting proximity effect at the nanometer scale. This effect will be used to study how the properties of the carbon-nanotube/normal-metal interface depend on the electrode material and on exposure to chemicals; and 3) The project will investigate the possible occurrence of superconductivity in individual single-walled carbon nanotubes when the gate voltage is applied. This effect will be studied in single nanotubes as well as in films of multiple nanotubes. The educational impact of this program goes well beyond the direct support of the postdoctoral fellow and the graduate student working on the project, as connections with this research are continuously developed in courses for non-science majors and physics majors.
