Events at Physics |
Events on Thursday, April 3rd, 2008
- R. G. Herb Condensed Matter Seminar
- Vortex dynamics in tailored superconducting channels: ratchets and circles
- Time: 10:00 am
- Place: 5310 Chamberlin
- Speaker: Britton Plourde, Syracuse University
- Abstract: The dynamics of vortex flow in confined geometries can be explored with tailored weak-pinning channels of superconducting a-NbGe surrounded by strong-pinning NbN channel edges. The lack of pinning allows the vortices to move through the channels with the dominant interaction determined by the shape of the channel walls. We have fabricated such weak-pinning channels with asymmetric sawtooth edges for controlling the motion of vortices. I will present our measurements of substantial asymmetries in the vortex dynamics in these channels, characteristic of a ratchet, and compare these with similar measurements on a set of channels with uniform width. We have also studied vortices flowing in circular channels arranged in a Corbino disk geometry. We have developed a SQUID voltmeter arrangement for resolving the flux flow voltage from a small number of vortices moving through such a single circular mesoscopic channel free from edge barriers.
- Host: McDermott
- NPAC (Nuclear/Particle/Astro/Cosmo) Forum
- Searching for double beta decay with the Enriched Xenon Observatory
- Time: 4:00 pm
- Place: 4274 Chamberlin Hall
- Speaker: Carter Hall, University of Maryland
- Abstract: An observation of neutrinoless double beta decay would have profound consequences for our understanding of the lepton sector of the standard model. Double beta decay is only allowed if the neutrino and anti-neutrino are identical, which is a basic prediction of many extensions of the standard model, including many grand unified theories. Secondly, double beta decay could shed light on the scale of the neutrino mass spectrum. The EXO collaboration is developing sensitive searches for the double beta decay of Xenon-136. Our first experiment, EXO-200, is rapidly being constructed, and will be by far the largest double beta decay experiment ever attempted. We are also pursuing R&D to realize a system to tag the daughter barium nucleus of the decay using the techniques of single-ion spectroscopy. This would eliminate all conventional backgrounds, resulting in an ideal experiment.