Events at Physics |
Events on Thursday, October 9th, 2008
- Yum Kippur
- R. G. Herb Condensed Matter Seminar
- Magnetotransport in Microwave-irradiated Quantum Hall Systems
- Time: 10:00 am
- Place: Chamberlin 5310
- Speaker: Michael Zudov, University of Minnesota
- Abstract: When a high quality two-dimensional electron system is irradiated by microwaves, its magnetoresistance exhibits microwave-induced resistance oscillations (MIRO) and zero-resistance states. MIRO were discussed in terms of the aEurooedisplacementaEuro model, which is based on microwave-assisted impurity scattering, and the aEurooeinelasticaEuro model, stepping from the oscillatory electron distribution function. It is believed that the aEurooeinelasticaEuro contribution greatly exceeds the aEurooedisplacementaEuro contribution and can also account for MIRO temperature dependence.
This talk will discuss our recent experiments focusing on non-linear response and temperature dependence of MIRO. First, we show that the aEuro~aEuroTMdisplacementaEuroTMaEuroTM mechanism cannot be ignored and might even dominate the response under typical experimental conditions. Further, we find that the MIRO temperature dependence originates primarily from the temperature-dependent quantum lifetime entering the Dingle factor. We suggest that the main source of the modification of the quantum scattering rate is the contribution from electron-electron scattering, a quantity hardly available from other experiments. - Host: Vavilov
- NPAC (Nuclear/Particle/Astro/Cosmo) Forum
- Neutron beta-decay with Ultra-Cold Neutrons
- Time: 4:00 pm
- Place: 4274 Chamberlin
- Speaker: Brad Filippone, Caltech
- Abstract: Ultra-Cold Neutrons - UCN - (E < 350 neV) can be trapped in material bottles and with magnetic fields. The UCNA collaboration has recently measured the beta-decay electron distribution from polarized neutron decay for the first time using UCN. The use of UCN suppresses a variety of systematic experimental effects compared to previous experiments using cold neutron beams. This allows for precision measurements of some Standard Model electroweak observables as well as searches for new physics. Results from this new experiment will be discussed along with prospects for future measurements.
- Host: Michael J Ramsey-Musolf