Events at Physics |
Events on Thursday, May 1st, 2008
- R. G. Herb Condensed Matter Seminar
- Magnetic 1/f noise from the semiconductor/oxide interface and spin-dependent scattering in silicon transistors
- Time: 10:00 am
- Place: 5310 Chamberlin
- Speaker: Rogerio de Sousa, University of Victoria
- Abstract: In the first part of the talk I will discuss a mechanism of magnetic noise based on spin-flips of paramagnetic dangling-bonds at the semiconductor/oxide interface. The spin-flips are caused by the cross-relaxation of dangling-bond spins with the tunnelling-two-level-systems of the amorphous interface, leading to magnetic 1/f noise even at zero magnetic field. I will compare and fit this model to a recent electron spin resonance experiment in nuclear-spin free silicon, and show that the same amount of interface noise detected by spin resonance may explain the intrinsic flux noise of the best superconducting quantum interference devices (SQUIDs).
In the second part I will describe a theory of spin-dependent scattering in the two-dimensional electron gas of silicon transistors. The scattering of conduction electrons off neutral donor impurities depends sensitively on the relative orientation of their spin states, and the six-fold degeneracy of the silicon conduction band leads to a strongly oscillatory coupling of conduction electrons to donors placed at varying depths in the transistor channel. This coupling can be gate controlled, enabling optimization for single donor spin readout and spatially resolved characterization of the conduction electron spin polarization that does not rely on weak spin-orbit coupling effects or interface scattering. - Host: Friesen
- NPAC (Nuclear/Particle/Astro/Cosmo) Forum
- Effective Field Theory of Light Nuclei
- Time: 4:00 pm
- Place: 4274 Chamberlin Hall
- Speaker: Bira van Kolck, University of Arizona
- Abstract: Nucleons in light nuclei have binding momenta smaller than the pion mass. In this energy regime, strong interactions can be described by effective field theories (EFTs) where all nuclear interactions are of contact type. I will discuss some of the features of these EFTs such as unusual renormalization leading to limit cycles, universal behavior in three-body systems, and a surprising amount of fine-tuning.
- Physics Department Colloquium
- Winner of the Distinguished Alumni Award 2008
- Exoplanet Detection and Characterization: Status and Prospects
- Time: 5:00 pm
- Place: 2241 Chamberlin Hall (coffee at 4:30 pm)
- Speaker: Wesley A. Traub, Jet Propulsion Lab
- Abstract: Nearly 300 exoplanets have been discovered in the past 13 years. We know the approximate mass and orbit of each of these, and for a few we have additional information about radius, composition, and temperature. However for most exoplanets we do not know these properties, nor do we know how they were formed, or whether any may have evolved like the Earth. The discovery of these unexpected exoplanets has ignited a whole new field of inquiry in astrophysics as well as physics and planetary science. One of the attractions is the prospect of finding an Earth-like planet, and searching for signs of life. Another attraction is the sheer joy of discovering and understanding a whole new part of our universe. In this talk I will outline the current measurement techniques and discoveries to date, but focus on future measurement techniques and what we may learn from them.