Center for Functional Nanomaterials Seminar

Shot noise is widely observed in everyday life, such as counting the number of rain drops falling into a bucket or the number of vehicles arriving at a parking lot in a given time interval. In electrical systems, shot noise is the time-dependent fluctuations in electrical currents due to the discreteness of the electron charge. It exists in various systems, including vacuum tubes, transistors, and nano-scale electronic devices. A powerful attribute of shot noise is that it reveals information on temporal correlations in electronic transport that is not accessible by typical transport investigations, such as current versus voltage measurements. In this talk, I will explore the exciting possibilities of studying shot noise in mesoscopic tunnel barriers using different measurement techniques. We first investigate the shot noise in single tunnel barriers and find that localized states in such systems have a significant effect on their shot noise behavior. By fabricating extremely small tunnel barriers, we are able to demonstrate theoretically predicted shot noise behavior of an ideal tunnel barrier that does not contain any localized state. We then perform shot noise cross spectrum measurements in a beam splitter configuration using tunnel barriers as electron sources. In certain cases, we find a surprising positive cross spectrum that is not expected to exist in electronic systems. Shot noise suppression due to quantum interference is also observed. I will end with a discussion of some interesting future possibilities, such as using shot noise to probe quantum entanglement.